Liquid crystal display device and electronic apparatus

ABSTRACT

The present invention provides a liquid crystal display device including a liquid crystal layer disposed between a first substrate and a second substrate, a pixel electrode in a reflection region and a transmission region over the first substrate, a film for adjusting a cell gap in the reflection region over the first substrate, and an opposite electrode in the reflection region and the transmission region over the second substrate. The pixel electrode in the reflection region is provided over the film and reflects light. The pixel electrode in the transmission region transmits light. The pixel electrode in the reflection region and the transmission region includes a slit. The slit is overlapped with at least a part of a step portion which is provided by the film between the reflection region and the transmission region.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a liquid crystal display deviceperforming a display of reflection type and transmission type, andparticularly to a liquid crystal display device performing a display ofa multi-domain mode.

2. Description of the Related Art

A liquid crystal display device is used for various electronic productssuch as a mobile phone, a monitor of navigation system, and atelevision. Some of these electronic products are used outside as wellas inside, and a semi-transmission type liquid crystal display device isknown, which includes both features of a transmission mode and areflection mode in order to ensure a high visibility both outside andinside.

As for a semi-transmission type liquid crystal display device, a displaydevice is known, which includes a pixel including a liquid crystalsandwiched between an active matrix substrate and an opposite substrate,a reflection portion performed a display of a reflecting mode and atransmission portion performed a display of a transmission mode (forexample, Reference 1: Japanese Published Patent Application No.2005-181981).

This liquid crystal display device includes an interlayer insulatingfilm for which a thickness of a liquid crystal layer of the reflectionportion is set to be substantially half of a thickness of a liquidcrystal layer of the transmission portion. In addition, this liquidcrystal display device includes an electrode coating which compensates adifference of work function because of a connection between a reflectingelectrode and a transparent electrode as an applied voltage adjustingunit in order to approximate voltages applied to the liquid crystal atthe reflection portion and the transmission portion close to each other.Further, the reflecting electrode and transparent electrode are providedwith a protruding portion, and the liquid crystal is formed to haveradial gradient orientation.

SUMMARY OF THE INVENTION

In the case where a liquid crystal is oriented in a radial gradientmanner, there is an advantage that a viewing angle is wide whendisplaying an image. However, there are a number of places wheredirections of orientation of liquid crystals are different; there areproblems that orientation control of a liquid crystal is difficult, adefect such as a disclination easily occurs, and image quality becomeslow. In particular, in the case of a pixel structure combining areflecting electrode with a transparent electrode such as a conventionalsemi-transmission type liquid crystal display device, there is a problemthat these defects are increased.

Therefore, the present invention provides a semi-transmission typeliquid crystal display device with high quality of display by improvinga viewing angle when displaying an image and by suppressingdeterioration of image quality due to disorder of orientation of theliquid crystal.

One feature of the invention is providing a liquid crystal displaydevice including a liquid crystal layer sandwiched between a pair ofsubstrates, which are arranged to oppose to each other, and formed of aliquid crystal molecule, a reflection region performing a display of areflecting mode, a transmission region performing a display of atransmission mode which are provided over one of the pair of substrates,and a pixel electrode provided with a slit portion between thereflection region and the transmission region. The liquid crystaldisplay device includes a cell gap adjusting film which is provided inthe reflection region so that a thickness of the liquid crystal layer issubstantially half of a thickness of the liquid crystal layer in thetransmission region. A reflection region of the pixel electrode isformed of a light-reflecting conductive film (reflection electrode) overthe cell gap adjusting film, and a transmission region thereof is formedof a transparent conductive film (transparent electrode). The slitportion is formed along a step portion (or a boundary portion) which isformed using by the cell gap adjusting film between the reflectionregion and the transmission region. Alternatively, the slit portion isextended radially to an oblique direction with respect to one endportion of the pixel electrode, and the step portion (or the boundaryportion) which is formed using by the cell gap adjusting film betweenthe reflection region and the transmission region is formed along theslit portion.

Orientation of a liquid crystal of the liquid crystal layer can becontrolled by providing the cell gap adjusting film in the reflectionregion performing a display of a reflecting mode, and overlapping thestep portion formed at the boundary portion of the cell gap adjustingfilm in accordance with the provision thereof with the slit portion ofthe pixel electrode.

That is, deterioration of image quality due to disorder of orientationof the liquid crystal can be controlled by using the boundary portion ofthe cell gap adjusting film or the step portion formed accompanying theboundary portion thereof, and the slit portion to control orientation ofthe liquid crystal and by preventing the control from counteracting andinterfering with each other.

In the aforementioned liquid crystal display device, a structure of theslit portion can be allowed some modifications. For example, an endportion on the transmission region side of the slit portion can beprovided apart from the step portion. In addition, the end portion onthe transmission region side of the slit portion can be located at theinside of a lower edge portion of the step portion. Further, an endportion of the transmission region can be provided below the cell gapadjusting film, the end portion on the transmission region side of theslit portion can be provided at the inside of a lower edge portion ofthe step portion.

In this manner, even if a structure of the slit portion of the pixelelectrode is changed, orientation of the liquid crystal of the liquidcrystal layer can be controlled by providing the cell gap adjusting filmin the reflection region performed a display of a reflecting mode, andoverlapping the step portion formed at the boundary portion of the cellgap adjusting film in accordance with the provision thereof with theslit portion of the pixel electrode.

In addition, an upper surface of the cell gap adjusting film may be anuneven surface, and the light-reflecting conductive film (reflectionelectrode) of the reflection region may be formed along with the unevensurface. By making a surface of the light-reflecting conductive film(reflection electrode) uneven, incident light is diffused, so that awhole luminance is averaged and a clear image can be obtained in thecase of displaying as a reflection type liquid crystal.

Another feature of the invention is providing a liquid crystal displaydevice including a liquid crystal layer which is sandwiched between apair of substrates, arranged to oppose to each other, and includes aliquid crystal molecule, a reflection region performing a display of areflecting mode and a transmission region performing a display of atransmission mode which are provided over one of the pair of substrates,and a pixel electrode provided with a slit portion between thereflection region and the transmission region. The liquid crystaldisplay device includes a cell gap adjusting film which is provided inthe reflection region so that a thickness of the liquid crystal layer issubstantially half of a thickness of the liquid crystal layer in thetransmission region. A reflection region of the pixel electrode isformed of a transparent conductive film formed over the cell gapadjusting film and a light-reflecting film formed over a lower layer ofthe cell gap adjusting film, and a transmission region thereof is formedof a transparent conductive film. The slit portion is formed along astep portion which is formed by using the cell gap adjusting filmbetween the reflection region and the transmission region.Alternatively, the slit portion is extended radially to an obliquedirection with respect to one end portion of the pixel electrode, andthe step portion which is formed using by the cell gap adjusting filmbetween the reflection region and the transmission region is formedalong the slit portion.

Orientation of a liquid crystal of the liquid crystal layer can becontrolled by providing the cell gap adjusting film in the reflectionregion performed a display of a reflecting mode, and forming areflection portion including the transparent conductive film formed overthe cell gap adjusting film and the light-reflecting film formed overthe lower layer of the cell gap adjusting film, and overlapping the stepportion of the cell gap adjusting film in accordance with the provisionthereof and the slit portion of the pixel electrode.

In the aforementioned liquid crystal display device, a structure of theslit portion can be allowed some modifications. For example, an endportion on the transmission region side of the slit portion can beprovided apart from the step portion. In addition, the end portion onthe transmission region side of the slit portion can be provided at theinside of a lower edge portion of the step portion. Further, the endportion of the transmission region can be provided on a lower layer sideof the cell gap adjusting film, and the end portion on the transmissionregion side of the slit portion can be provided at the inside of a loweredge portion of the step portion.

In this manner, even if a structure of the slit portion of the pixelelectrode is changed, orientation of the liquid crystal of the liquidcrystal layer can be controlled by providing the cell gap adjusting filmin the reflection region performed a display of a reflecting mode, andoverlapping the step portion formed at the boundary portion of the cellgap adjusting film in accordance with the provision thereof and the slitportion of the pixel electrode.

In addition, a lower surface of the cell gap adjusting film may be anuneven surface, and a light-reflecting film of the reflection region maybe formed along with the uneven surface. By making a surface of thelight-reflecting film uneven, an incident light is diffused; therefore,a whole luminance is averaged and a clear image can be obtained in thecase of display as a reflection type liquid crystal. In that case,disorder of orientation of the liquid crystal does not happen because anupper surface of the cell gap adjusting film may be even, by whichdeterioration of image quality due to disorder of orientation of theliquid crystal can be controlled.

In addition, in the invention, a strip-shaped protruding portion in anoblique direction with respect to an edge portion of the pixel electrodeis provided with a structure of the aforementioned liquid crystaldisplay device, and a liquid crystal display device of so-calledmulti-domain vertical alignment (MVA) type can be formed. Such astructure can also be obtained the same operation effect as describedabove.

In accordance with multi-domain, that is, having a plurality of regions,there is a plurality of directions in which liquid crystal molecules areinclined, and the ways the liquid crystal molecules look are averagedeven when seen from any direction; therefore, a characteristic ofviewing angle can be improved.

Note that a strip-shaped slit portion may be provided instead of thestrip-shaped protruding portion in the oblique direction with respect tothe edge portion of the pixel electrode. In addition, the strip-shapedslit portion may be provided over one substrate, and the strip-shapedprotruding portion may be provided over the other substrate with theliquid crystal sandwiched therebetween.

Another feature of the invention is providing a liquid crystal displaydevice including a liquid crystal layer disposed between a firstsubstrate and a second substrate, a pixel electrode in a reflectionregion and a transmission region over the first substrate, a film foradjusting a cell gap in the reflection region over the first substrate,and an opposite electrode in the reflection region and the transmissionregion over the second substrate. The pixel electrode in the reflectionregion is provided over the film and reflects light. The pixel electrodein the transmission region transmits light. The pixel electrode in thereflection region and the transmission region includes a slit. The slitis overlapped with at least a part of a step portion which is providedby the film between the reflection region and the transmission region.

Note that in the invention, being connected is synonymous with beingelectrically connected. Therefore, in addition to a predeterminedrelation of connection, another element which enables an electricalconnection (for example, a switch, a transistor, a capacitor, aninductor, a resistor element, a diode, or the like) may be provided in astructure disclosed by the invention. Components may be provided withoutthrough another element as well, and being electrically connectedincludes the case of being directly connected. Note that an element ofvarious forms may be used as a switch, such as an electrical switch anda mechanical switch. That is, any element which can control a flow ofcurrent may be employed, and it is not limited to a specific form of aswitch. For example, a transistor, a diode (a PN diode, a PIN diode, aschottky diode, a diode-connected transistor, or the like), or a logiccircuit combined therewith may be used. In the case of using atransistor as a switch, a polarity (conductivity type) thereof is notspecifically limited since the transistor is operated as a mere switch.However, a transistor with small OFF current is preferably used. As fora transistor with small OFF current, a transistor provided with an LDDregion, a transistor with a multi-gate structure, or the like may beused. In addition, it is preferable to use an n-channel transistor whenoperating in a state where a potential of a source electrode of thetransistor, which operates as a switch, is close to a low potential sidepower source (Vss, GND, 0V or the like), whereas it is preferable to usea p-channel transistor when operating in a state where a potential of asource electrode of the transistor is close to a high potential sidepower source (Vdd or the like). This is because it is easily operated asa switch since an absolute value of a gate-source voltage thereof can bemade to be large. Note that a CMOS type switch may also be applied byusing both n-channel and p-channel transistors. In the case where a CMOStype switch is employed, the switch can be operated properly since anoutput voltage is easily controlled with respect to various inputvoltages.

Note that a transistor is an element having at least three terminalsincluding a gate electrode, a drain region, and a source region. Achannel forming region is provided between the drain region and thesource region. Here, it is difficult to precisely define the sourceregion and the drain region since they depend on a structure, operatingconditions, and the like of the transistor. Therefore, in the case ofexplaining a relation of connection of a transistor, concerning twoterminals of the source region and the drain region, one of electrodesconnected to these regions is referred to as a first electrode, and theother electrode is referred to as a second electrode, which may be usedfor explanation. Note that a transistor may be an element having atleast three terminals including a base, an emitter, and a collector.Similarly, in this case, the emitter and the collector may be called afirst electrode and a second electrode, respectively.

Noted that a structure of a transistor can have various modes and is notlimited to a specific structure. For example, a multi-gate structurewhere the number of gates is two or more may be employed. With amulti-gate structure, an OFF current can be reduced and reliability canbe improved by improving the pressure resistance of a transistor, and achange of current flowing between a drain and a source in accordancewith a change of voltage between a drain and a source can be reducedwhen operating in a saturation region. Further, gate electrodes may beprovided over and under a channel. By a structure where gate electrodesare provided over and under a channel, a channel region increases,thereby a current value is increased, and a subthreshold value (S value)can be improved since a depletion layer is easily formed. Further, agate electrode may be provided over or under the channel. Either aforward staggered structure or an inversely staggered structure may beemployed. A channel region may be divided into a plurality of regions,or connected in parallel or in series. Further, a source electrode or adrain electrode may overlap with a channel (or a part thereof), therebypreventing a charge from being accumulated in a part of the channel andoperating unstably. Further, an LDD region may be provided. By providingan LDD region, an OFF current can be reduced and reliability can beimproved by improving the pressure resistance of a transistor, and acharacteristic that a drain-source current does not change much evenwhen a drain-source voltage changes when operating in a saturationregion can be obtained.

Note that a gate includes a gate electrode and a gate wire (alsoreferred to as a gate line, a gate signal line, or the like) or a partthereof. Note that a gate electrode corresponds to a part of aconductive film overlapping with a semiconductor, in which a channelregion is formed, with a gate insulating film sandwiched therebetween. Agate wire corresponds to a wire for connecting gate electrodes of pixelsand for connecting a gate electrode and another wire.

However, there is also a portion which functions both as a gateelectrode and as a gate wire. That is, there is a region which cannot bespecifically distinguished between a gate electrode and a gate wire. Forexample, in the case of a channel region overlapping with a gate wirewhich is extended, the region functions as a gate wire and also as agate electrode. Therefore, such a region may be referred to as a gateelectrode or a gate wire.

In addition, a region which is formed of the same material as a gateelectrode and connected to the gate electrode may be called a gateelectrode as well. Similarly, a region which is formed of the samematerial as a gate wire and connected to the gate wire may be called agate wire. In a strict sense, such a region does not overlap a channelregion or does not have a function to connect to another gate electrodein some cases. However, there is a region which is formed of the samematerial as a gate electrode or a gate wire and connected to the gateelectrode or the gate wire due to a manufacturing margin and the like.Therefore, such a region may be called a gate electrode or a gate wire.

In addition, for example, in a multi-gate transistor, a gate electrodeof one transistor and a gate electrode of another transistor are oftenconnected with a conductive film formed of the same material as the gateelectrode. Such a region may be called a gate wire since it is a regionfor connecting the gate electrodes, or may be called a gate electrodesince a multi-gate transistor can be considered as one transistor. Thatis, a component which is formed of the same material as a gate electrodeor a gate wire and connected to the gate electrode or the gate wire maybe called a gate electrode or a gate wire. Further, for example, a partof a conductive film which connects a gate electrode and a gate wire maybe called a gate electrode or a gate wire.

Note that a gate terminal corresponds to a part of a region of a gateelectrode or a region electrically connected to a gate electrode.

Note that a source corresponds to a source region, a source electrode,and a source wire (also referred to as a source line, a source signalline, or the like), or a part thereof. A source region corresponds to asemiconductor region which contains a large amount of a P-type impurity(boron, gallium, or the like) or an N-type impurity (phosphorus,arsenic, or the like). Therefore, a region containing a small amount ofa P-type impurity or an N-type impurity, that is, an LDD (Lightly DopedDrain) region is not included in a source region. A source electrodecorresponds to a conductive layer which is formed of a differentmaterial from a source region and electrically connected to the sourceregion. However, a source electrode including a source region may becalled a source electrode. A source wire corresponds to a wire forconnecting source electrodes of pixels and for connecting a sourceelectrode and another wire.

However, there is a part which functions both as a source electrode andas a source wire. That is, there is a region which cannot bespecifically distinguished between a source electrode and a source wire.For example, when there is a source region overlapping a source wirewhich is extended, the region functions both as a source wire and as asource electrode. Therefore, such a region may be called a sourceelectrode or a source wire.

Further, a region which is formed of the same material as a sourceelectrode and connected to the source electrode, or a connecting portionof the source electrodes may be called a source electrode as well. Aportion overlapping a source region may be called a source electrode.Similarly, a region which is formed of the same material as a sourcewire and connected to the source wire may be called a source wire. In astrict sense, such a region does not have a function to connect toanother source electrode in some cases. However, there is a region whichis formed of the same material as a source electrode or a source wireand connected to a source electrode or a source wire due to amanufacturing margin and the like. Therefore, such a region may also becalled a source electrode or a source wire.

In addition, for example, a portion of a conductive film which connectsa source electrode and a source wire may be called a source electrode ora source wire.

Note that the same as a source is applied to a drain, and descriptionthereof is omitted.

In the specification, pixels may be arranged in matrix. Here, the casewhere pixels are arranged in matrix corresponds to the cases wherepixels are arranged in a straight line and a jagged line in alongitudinal direction or a lateral direction. Therefore, in the case ofperforming a full color display with three color elements (for example,RGB), an arrangement of pixels may include the case of arranging instripes and the case where pixels of the three color elements arearranged in a so-called delta pattern. Further, a Bayer pattern may beincluded.

Note that in the invention one pixel corresponds to one element whichcan control brightness. Therefore, for example, one pixel denotes onecolor element by which brightness is expressed. Accordingly, in the caseof a color display device formed of color elements of R (red), G(green), and B (blue), the smallest unit of an image is formed of threepixels of an R pixel, a G pixel, and a B pixel. Note that the number ofcolor of color elements is not limited to three colors and may be formedof more than three colors such as RGBW (W is white) and RGB to whichyellow, cyan, and magenta are added.

In addition, as another example, in the case of controlling thebrightness of one color element by using a plurality of regions, one ofthe plurality of regions corresponds to one pixel. However, the case ofemploying a subpixel is excluded. For example, in the case of performingan area gray scale display, a plurality of regions for controlling thebrightness are provided for one color element, which express a grayscale as a whole, and one of the regions for controlling the brightnesscorresponds to one pixel. Therefore, in this case, one color element isformed of a plurality of pixels. Moreover, in this case, a region whichcontributes to a display may differ in size depending on pixels. In theplurality of pixels forming one color element, a viewing angle may beexpanded by supplying a slightly different signal to each pixel.

Note that in the specification, a semiconductor device corresponds to adevice including a circuit which has a semiconductor element (atransistor, a diode, or the like). Further, a semiconductor device maybe a general device which can operate by using semiconductorcharacteristics. A display device corresponds to a device including adisplay element (a liquid crystal element, a light emitting element, orthe like). Note that a display device may be a main body of a displaypanel in which a plurality of pixels including a display element such asa liquid crystal element or an EL element and a peripheral drivercircuit for driving the pixels are formed over a substrate. Further, adisplay device may include an element (an IC, a resistor, a capacitor,an inductor, a transistor, or the like) which is provided with aflexible printed circuit (FPC) or a printed wiring board (PWB). Adisplay device may include an optical sheet such as a polarizing plateor a retardation film. In addition, a backlight (such as a lightconductive plate, a prism sheet, a diffusion sheet, a reflection sheet,a light source (LED, cold-cathode tube, or the like) may be included.

Note that in the display device of the invention various modes andvarious display elements can be applied. For example, a display mediumin which contrast is changed by an electromagnetic effect can be used,such as an EL element (an organic EL element, an inorganic EL element,or an EL element containing an organic material and an inorganicmaterial), an electron-emissive element, electronic ink, a grating lightvalve (GLV), a plasma display (PDP), a digital micromirror device (DMD),a piezoelectric ceramic display, or a carbon nanotube in addition to aliquid crystal element. Note that a display device using an EL elementincludes an EL display; a display device using an electron-emissiveelement includes a field emission display (FED), an SED type flat paneldisplay (Surface-conduction Electron-emitter Display), and the like; adisplay device using a liquid crystal element includes a liquid crystaldisplay, a transmission type liquid crystal display, a semi-transmissiontype liquid crystal display, a reflection type liquid crystal display;and a display device using electronic ink includes electronic paper.

Note that in the invention, when it is described that an object isformed on another object, it does not necessarily mean that the objectis in direct contact with the another object. The case where two objectsare not in direct contact with each other, that is, the case where otherobject is sandwiched therebetween may also be included. Accordingly,when it is described that a layer B is formed on a layer A, for example,it means either the case where the layer B is formed in direct contactwith the layer A, or the case where another layer (such as a layer C ora layer D) is formed in direct contact with the layer A and then thelayer B is formed in direct contact with the another layer. In addition,when it is described that an object is formed over or above anotherobject, it is not limited in the case where the object is in directcontact with the another object and still another object may besandwiched therebetween. Accordingly, when it is described that a layerB is formed over or above a layer A, for example, it means either thecase where the layer B is formed in direct contact with the layer A, orthe case where another layer (such as a layer C or a layer D) is formedin direct contact with the layer A and then the layer B is formed indirect contact with the another layer. Similarly, when it is describedthat an object is formed below or under another object, it means eitherthe case where the objects are in direct contact with each other or notin contact with each other.

Orientation of a liquid crystal can be controlled by providing a cellgap adjusting film in a reflection region of a pixel electrode, andproviding a step portion thereof (a boundary portion of the cell gapadjusting film) so as to overlap in parallel with a slit portion at aboundary portion between a reflection region and a transmission region.Therefore, a semi-transmission type liquid crystal display device withhigh display quality can be obtained by improving a viewing angle whendisplaying an image and by suppressing deterioration of image qualitydue to disorder of orientation of the liquid crystal.

BRIEF DESCRIPTION OF DRAWINGS

FIGS. 1A and 1B are diagrams showing a structure of a display device ofthe invention.

FIGS. 2A to 2C are diagrams showing a structure of a display device ofthe invention.

FIGS. 3A and 3B are diagrams showing a structure of a display device ofthe invention.

FIGS. 4A and 4B are diagrams showing a structure of a display device ofthe invention.

FIGS. 5A and 5B are diagrams showing a structure of a display device ofthe invention.

FIGS. 6A and 6B are diagrams showing a structure of a display device ofthe invention.

FIGS. 7A and 7B are diagrams showing a structure of a display device ofthe invention.

FIGS. 8A and 8B are diagrams showing a structure of a display device ofthe invention.

FIGS. 9A and 9B are diagrams showing a structure of a display device ofthe invention.

FIGS. 10A and 10B are diagrams showing a structure of a display deviceof the invention.

FIGS. 11A and 11B are diagrams showing a structure of a display deviceof the invention.

FIGS. 12A and 12B are diagrams showing a structure of a display deviceof the invention.

FIGS. 13A and 13B are diagrams showing a structure of a display deviceof the invention.

FIGS. 14A and 14B are diagrams showing a structure of a display deviceof the invention.

FIGS. 15A to 15D are diagrams showing a structure of a display device ofthe invention.

FIGS. 16A and 16B are diagrams showing a structure of a display deviceof the invention.

FIGS. 17A and 17B are diagrams showing a structure of a display deviceof the invention.

FIG. 18 is a diagram showing a structure of a display device of theinvention.

FIG. 19 is a diagram showing a structure of a display device of theinvention.

FIG. 20 is a plan layout view showing a display device of the invention.

FIG. 21 is a cross sectional view showing a display device of theinvention.

FIG. 22 is a plan layout view showing a display device of the invention.

FIG. 23 is a cross sectional view showing a display device of theinvention.

FIG. 24 is a plan layout view showing a display device of the invention.

FIG. 25 is a plan layout view showing a display device of the invention.

FIG. 26 is a plan layout view showing a display device of the invention.

FIG. 27 is a plan layout view showing a display device of the invention.

FIG. 28 is a plan layout view showing a display device of the invention.

FIG. 29 is a cross sectional view showing a display device of theinvention.

FIG. 30 is a cross sectional view showing a display device of theinvention.

FIG. 31 is a cross sectional view showing a display device of theinvention.

FIG. 32 is a cross sectional view showing a display device of theinvention.

FIG. 33 is a cross sectional view showing a display device of theinvention.

FIG. 34 is a cross sectional view showing a display device of theinvention.

FIG. 35 is a cross sectional view showing a display device of theinvention.

FIGS. 36A to 36C are diagrams showing a manufacturing flow of a displaydevice of the invention.

FIGS. 37A to 37D are diagrams showing a manufacturing flow of a displaydevice of the invention.

FIGS. 38A to 38C are diagrams showing a manufacturing flow of a displaydevice of the invention.

FIGS. 39A to 39D are diagrams showing a manufacturing flow of a displaydevice of the invention.

FIGS. 40A to 40D are diagrams showing a manufacturing flow of a displaydevice of the invention.

FIGS. 41A to 41D are diagrams showing a manufacturing flow of a displaydevice of the invention.

FIGS. 42A and 42B are diagrams showing a manufacturing flow of a displaydevice of the invention.

FIGS. 43A and 43B are cross sectional views showing a display device ofthe invention.

FIG. 44 is a diagram showing an electronic apparatus to which theinvention is applied.

FIGS. 45A and 45B are diagrams showing an electronic apparatus to whichthe invention is applied.

FIG. 46 is a diagram showing an electronic apparatus to which theinvention is applied.

FIG. 47 is a diagram showing an electronic apparatus to which theinvention is applied.

FIGS. 48A to 48H are diagrams showing an electronic apparatus to whichthe invention is applied.

FIGS. 49A to 49F are diagrams showing a structure example of a pixel towhich the invention is applied.

DETAILED DESCRIPTION OF THE INVENTION

Although the invention will be fully described by embodiment modes withreference to the accompanying drawings, it is to be understood thatvarious changes and modifications will be apparent to those skilled inthe art. Therefore, unless such changes and modifications depart fromthe spirit and the scope of the invention, they should be construed asbeing included therein. Note that in a structure of the inventiondescribed below, a reference numeral denoting the same component in adifferent drawing is used commonly, and description thereof may beomitted.

Embodiment Mode 1

In this embodiment mode, description is made of a structure of asemi-transmission type liquid crystal (which includes a reflectionregion and a transmission region in one pixel, and can be employed bothas a transmission type liquid crystal and a reflection type liquidcrystal) employing a vertically aligned liquid crystal, which hasdifferent cell gaps (a distance between two electrodes arranged to faceeach other through a liquid crystal) of a liquid crystal in thetransmission region and the reflection region, so that a display can beperformed normally. A light entering a liquid crystal is passed throughthe liquid crystal twice in the reflection region, and a light is passedthrough the liquid crystal once in the transmission region. Therefore,it is required to perform a similar display in the case of performing adisplay as the transmission type liquid crystal and in the case ofperforming a display as the reflection type liquid crystal, and a cellgap in the reflection region is made nearly half of a cell gap in thetransmission region so that distances where the light is passed throughthe liquid crystal are almost the same. As a method for reducing thecell gap in the reflection region, a film is provided as a spacer in thereflection region. Hereinafter, this film is also referred to as a cellgap adjusting film or a film for adjusting a cell gap.

Note that the cell gap in the transmission region corresponds to adistance between a transparent electrode and an electrode on an oppositeside across the liquid crystal, while the cell gap in the reflectionregion corresponds to a distance between an electrode (there are thecase of the transparent electrode and the case of an reflectionelectrode) over the cell gap adjusting film and an electrode of anopposite side across the liquid crystal. In the case where an electrodeis uneven, the distance is calculated using an average of a high partand a low part thereof.

In the case of the vertically aligned liquid crystal, liquid crystalmolecules stand perpendicularly to a substrate when a voltage is notapplied to the liquid crystal, and the liquid crystal molecules areinclined in a parallel direction when a voltage is applied to the liquidcrystal. At that time, the way an electric field is applied and apretilt angle of the liquid crystal molecules are required to becontrolled in order to control a direction that the liquid crystal isinclined.

As a method for controlling a direction that the liquid crystal isinclined when a voltage is applied, a gap like a slit is made at anelectrode, so that an electric field is supplied in a slightly-curveddirection with respect to an up-and-down direction (the same directionas the liquid crystal vertically aligned, and a vertical direction tothe substrate and the electrode). For example, in the case where oneelectrode for applying an electric field to the liquid crystal isprovided over a whole region, the electric field is applied in anup-and-down direction appropriately because the electric field isequally applied. However, when an electrode is provided with a gap likea slit and a space, the electric field curves slightly. The liquidcrystal molecules are controlled in accordance with an electric fieldand incline in a parallel direction in accordance with a direction ofthe electric field. Accordingly, distortion of the electric field isused for controlling a direction that the vertically aligned liquidcrystal molecules are inclined when a voltage is applied. Therefore, itcan be prevented from a defective display due to an orientation defectcaused by the inclination of the liquid crystal molecules in variousdirections.

As another method for controlling a direction that the liquid crystalmolecules are inclined, a projection (a protruding portion) is providedover an electrode portion. The pretilt angle of the liquid crystalmolecules changes along with a projection when provided. Accordingly,the liquid crystal molecules incline slightly even in condition that theelectric field is not supplied to the liquid crystal; therefore, thedirection that the liquid crystal molecules are inclined can becontrolled in accordance with a slightly-inclined direction when avoltage is supplied.

Meanwhile, a cell gap adjusting film is provided in the reflectionregion in order that the transmission region and the reflection regionhave different cell gaps of the liquid crystal. The cell gap adjustingfilm is thick, therefore influencing a direction that the verticallyaligned liquid crystal molecules are inclined. Therefore, it is requiredto avoid disordering orientation of the liquid crystal molecules andcausing a disclination in a boundary portion between the transmissionregion and the reflection region (or a step portion formed by the cellgap adjusting film).

FIGS. 1A and 1B show a relation between a reflection electrode 101, atransparent electrode 102, and a slit 105 (a gap, a space, or the like)of an electrode, and a cell gap adjusting film 103. FIG. 1A is a topplan layout view. FIG. 1B is a cross sectional view taken a line A1-A1′in FIG. 1A. As shown in FIG. 1A, in the case where the reflectionelectrode 101, the transparent electrode 102, the slit 105 (the gap, thespace, or the like) of the electrode are provided, the reflectionelectrode 101 and the transparent electrode 102 are arrangedapproximately in parallel. Therefore, the slit 105 (the gap, the space,or the like) of the electrode, which is formed by the reflectionelectrode 101 and the transparent electrode 102, is also arrangedapproximately in parallel. The cell gap adjusting film 103 (a boundaryportion or a step portion thereof) is provided to be arrangedapproximately in parallel therewith. The boundary portion (or the stepportion) of the cell gap adjusting film 103 is provided between thereflection electrode 101 and the transparent electrode 102. As shown inFIG. 1B, the cell gap adjusting film 103 is formed over a lower layer104, the reflection electrode 101 is formed over the cell gap adjustingfilm 103, and the transparent electrode 102 is formed over the lowerlayer 104.

As shown in FIG. 1B, liquid crystal molecules 106 are oriented byproviding the slit 105 (the gap, the space, or the like) of theelectrode and a protrusion of the cell gap adjusting film 103. Adirection of inclination of the liquid crystal molecules 106 in the casewhere only the slit 105 (the gap, the space, or the like) of theelectrode is provided and a direction of inclination thereof in the casewhere only the cell gap adjusting film 103 is provided are almost thesame. The direction of inclination of the liquid crystal molecules 106by providing the slit 105 is almost the same as the direction ofinclination of the liquid crystal molecules 106 by providing the cellgap adjusting film 103, therefore not disturbing each other. The liquidcrystal is oriented appropriately, and disorder of orientation thereofhardly happens.

As shown in FIG. 1A, a direction of the liquid crystal is arranged inone direction by arranging the slit 105 (the gap, the space, or thelike) of the electrode and the boundary portion (or the step portion) ofthe cell gap adjusting film 103 in parallel; therefore, orientation ofthe liquid crystal molecules 106 is hardly disordered.

In the case where the liquid crystal molecules are inclined and in aradial pattern from one point as a flower blooms, a region in which mostof the liquid crystal molecules inclined to various directions is madeat a boundary with another adjacent region; therefore, disorder oforientation of the liquid crystal molecules may occur. In addition, inthe case where the cell gap adjusting film is provided, orientation ofthe liquid crystal is affected, so that disorder thereof may be worse.However, in the invention, the liquid crystal is aligned in a regionextended in parallel, so that a region in which liquid crystal moleculesinclined to various directions gather is hardly made, and disorder oforientation of the liquid crystal molecules hardly occurs.

Note that the lower layer 104 may have various structures. A transistor,an interlayer film, glass, and the like may be provided. A color filter,a black matrix, and the like may be provided. In addition, the lowerlayer 104 is not required to be even. Further, a transistor may beprovided over an opposite substrate but not over the lower layer 104with the liquid crystal sandwiched between the opposite substrate andthe lower layer 104.

The slit 105 (the gap, the space, or the like) of the electrode, thereflection electrode 101, the transparent electrode 102, and theboundary portion (or the step portion) of the cell gap adjusting film103 is not required to be perfectly parallel as a part thereof or as awhole. A space, a distance and a position thereof may be changed to someextent depending on a place if an operation is not affected.

In the case where the slit 105 (the gap, the space, or the like) of theelectrode, the reflection electrode 101, the transparent electrode 102,and the boundary portion (or the step portion) of the cell gap adjustingfilm 103 are provided in parallel, a length of a part in paralleltherewith is not limited as long as it is longer than at least a widthof the slit 105 (the gap, the space, or the like) of the electrode. Notethat it is preferably provided as long as possible in a pixel pitch.

The reflection electrode 101 is acceptable as long as it reflects light.Therefore, the transparent electrode may be provided above or below thereflection electrode. That is, a stacked structure can be used for anelectrode. A stacked structure can be used for a part of the reflectionelectrode 101 or as a whole.

The reflection electrode 101 and the transparent electrode 102 areelectrically connected and operated as one electrode for the liquidcrystal; therefore, the reflection electrode 101 and the transparentelectrode 102 are required to be electrically connected. Accordingly,when the reflection electrode 101 is provided only over the cell gapadjusting film 103 or when the transparent electrode 102 is not providedover the cell gap adjusting film 103, the reflection electrode 101 andthe transparent electrode 102 cannot be electrically connected. Thus, asshown in FIGS. 2A to 2C, the reflection electrode 101 may be extendedbelow the cell gap adjusting film 103 or the transparent electrode 102may be extended above the cell gap adjusting film 103 in order that thereflection electrode 101 and the transparent electrode 102 areelectrically connected. FIG. 2A is a top plan layout view. FIG. 2B is across sectional view taken a line A1-A1′ in FIG. 2A. FIG. 2C is a crosssectional view taken a line A2-A2′ in FIG. 2A. As shown in FIG. 2C, anelectrode 201 is either the reflection electrode 101 or the transparentelectrode 102, and becomes either a transmission electrode or areflection electrode from a certain region. Therefore, the number oflayers may be increased in the middle of a region.

That is, the transparent electrode 102 may be in contact with a part ofthe reflection electrode 101 or a whole.

Note that in one pixel, it is not preferable that the reflectionelectrode 101 and the transparent electrode 102 are in a floating statealthough an electric field is desired to be applied to the liquidcrystal. Therefore, as shown in FIGS. 2A and 2C, at least a part of thereflection electrode and at least a part of the transparent electrodemay be electrically connected. As shown in FIGS. 2B, 1A and 1B, thereflection electrode 101 and the transparent electrode 102 may beprovided separately, and a slit (a gap, a space, or the like ofelectrodes) may be provided therebetween.

Next, the description is made of a distance between the reflectionelectrode 101 and the transparent electrode 102, and the boundaryportion of the cell gap adjusting film 103. The liquid crystal molecules106 is controlled by using the transparent electrode 102 of atransmission region. As a method for controlling a direction that theliquid crystal molecules are inclined, both the slit 105 (the gap, thespace, or the like) of the electrode and the cell gap adjusting film 103are used. As shown in FIGS. 3A and 3B, a distance d2 between theboundary portion of the cell gap adjusting film 103 and the transparentelectrode 102 may be short.

On the other hand, liquid crystal molecules 306 are controlled by usingthe reflection electrode 101. As a method for controlling a directionthat the liquid crystal molecules 306 are inclined, only the slit 105(the gap, the space, or the like) of the electrode is used. Therefore, adistance d1 between the boundary portion of the cell gap adjusting film103 and the reflection electrode 101 is required to be large. In thecase where the distance d1 is small, the liquid crystal molecules may beinclined to an undesirable direction since the liquid crystal molecules306 are not fully controlled by the reflection electrode 101. In view ofthe above, the distance d1 between the boundary portion of the cell gapadjusting film 103 and the reflection electrode 101 is preferably largerthan the distance d2 between the boundary portion of the cell gapadjusting film 103 and the transparent electrode 102.

In addition, as a relation to a thickness d3 of the cell gap adjustingfilm, the thickness d3 of the cell gap adjusting film is preferablysmaller than the distance d1 between the boundary portion of the cellgap adjusting film 103 and the reflection electrode 101. By making thedistance d1 between the boundary portion of the cell gap adjusting film103 and the reflection electrode 101 larger than the thickness d3 of thecell gap adjusting film, an upper surface of the cell gap adjusting film103 is made to be even, and the liquid crystal molecules 306 can befully controlled.

The liquid crystal molecules 106 are controlled by using the transparentelectrode 102 of the transmission region. As a method for controlling adirection that the liquid crystal molecules 106 are inclined, both theslit 105 (the gap, the space, or the like) of the electrode and the callgap adjusting film 103 are used. Therefore, the distance d2 between theboundary portion of the cell gap adjusting film 103 and the transparentelectrode 102 may be small, or the distance d2 may be zero. In addition,instead of providing the boundary portion of the cell gap adjusting film103 between the reflection electrode 101 and the transparent electrode102, the transparent electrode 102 may be provided between thereflection electrode 101 and the boundary portion of the cell gapadjusting film 103 as shown in FIGS. 4A and 4B. Since both the slit 105(the gap, the space, or the like) of the electrode and the cell gapadjusting film 103 are used as a method for controlling the directionthat the liquid crystal molecules 106 are inclined, the liquid crystalmolecules 106 are oriented appropriately without any problems even inthe case where the transparent electrode 102 is provided between thereflection electrode 101 and the boundary portion of the cell gapadjusting film 103 as shown in FIGS. 4A and 4B.

Although FIGS. 4A and 4B are diagrams showing the transparent electrode102 formed over the cell gap adjusting film 103, a structure is notlimited to this. The transparent electrode 102 may be provided below thecell gap adjusting film 103 as shown in FIGS. 5A and 5B. Note that FIGS.4A and 5A are top plan layout views. FIGS. 4B and 5B are cross sectionalviews taken a line A1-A1′ in FIGS. 4A and 5A, respectively.

A distance d2′ between the boundary portion of the cell gap adjustingfilm 103 and the transparent electrode 102 is preferably smaller thanthe thickness d3 of the cell gap adjusting film. That is because d2′ isincluded in the reflection region completely when d2′ is larger than d3.

The cell gap adjusting film is preferably formed of a materialcontaining an organic material because of need for a certain thickness.The material containing an organic material preferably includes acrylic,polyimide, or polycarbonate, for example. A thickness of the cell gapadjusting film is preferably approximately half the cell gap of theliquid crystal because a distance where light is passed through theliquid crystal portion is preferably the same in the reflection regionand the transmission region. Note that it is not required to be thecomplete half thereof since light often enters obliquely. It ispreferably about half the cell gap of the liquid crystal within a rangeof approximately ±10%. Since the cell gap of the liquid crystal is 3 to6 μm, the thickness d3 of the cell gap adjusting film is preferably 1.1to 3.3 μm. However, the thickness of the cell gap adjusting film is notlimited to this, and the cell gap adjusting film may have a thicknesswhich can provide a similar effect.

The transparent electrode 102 is preferably formed of a conductivematerial with high transmissivity because it is required to transmitlight. Indium oxide-tin oxide (ITO, Indium Tin Oxide), indium oxide-zincoxide (IZO), or polysilicon is preferably used, for example. Thereflection electrode 101 is preferably formed of a conductive materialwith high reflectivity because it is required to reflect light. Al, Ti,or Mo is preferably used, for example. The distance d2 between theboundary portion of the cell gap adjusting film 103 and the transparentelectrode 102 is preferably 0 to 1.1 μm. The distance d2′ between theboundary portion of the cell gap adjusting film 103 and the transparentelectrode 102 is preferably 0 to 1.1 μm. The distance d1 between theboundary portion of the cell gap adjusting film 103 and the reflectionelectrode 101 is preferably 1.1 to 6 μm since most of the reflectionelectrode 101 is preferably formed over the cell gap adjusting film 103.However, it is not limited to this.

Embodiment Mode 2

This embodiment mode describes an example other than the case where thereflection electrode 101 is formed over the cell gap adjusting film 103described in Embodiment mode 1.

FIG. 6A is a top plan layout view. FIG. 6B is a cross sectional view ofFIG. 6A. As shown in FIG. 6A, in the case where a reflection electrode601, a transparent electrode 602, a transparent electrode 102, a slit605 (a gap, a space, or the like) of an electrode are provided, thereflection electrode 601, the transparent electrode 602 and thetransparent electrode 102 are arranged approximately in parallel, andthe slit 605 (the gap, the space, or the like) of the electrode is alsoarranged in parallel. A cell gap adjusting film (a boundary portionthereof) 103 is arranged approximately in parallel therewith. Theboundary portion of the cell gap adjusting film 103 is provided betweenthe reflection electrode 601 and the transparent electrode 102. As shownin FIG. 6B, the reflection electrode 601 is formed over a lower layer104, over which the cell gap adjusting film 103 is formed. Thetransparent electrode 602 is formed over the lower layer 104.

Light is reflected by the reflection electrode 601 in a reflectionregion, therefore light passes through the cell gap adjusting film 103.However, in view of a refractive index, a polarization state of light isnot changed because the cell gap adjusting film 103 is made of anisotropic material. Therefore, light is hardly affected even whenpassing through the cell gap adjusting film 103. A liquid crystal iscontrolled by using the transparent electrode 602 over the cell gapadjusting film 103.

The transparent electrode 602 and the transparent electrode 102 arepreferably electrically connected so as to function as one pixelelectrode and to supply an electric field to the liquid crystal. On theother hand, the reflection electrode 601 is not required to beelectrically connected to the transparent electrode 602 and thetransparent electrode 102 because it is provided for reflecting light.However, in the case where the reflection electrode 601 is used as anelectrode for a storage capacitor, the reflection electrode 601 may beelectrically connected to the transparent electrode 602 and thetransparent electrode 102.

A distance d1′ between the boundary portion of the cell gap adjustingfilm 103 and the transparent electrode 602 is preferably approximatelythe same as a distance d1 between the boundary portion of the cell gapadjusting film 103 and the reflection electrode 601. Note that it ispreferable that the reflection electrode 601 is larger than thetransparent electrode 602 which controls liquid crystal moleculesbecause it can reflect more light. The distance d1′ between the boundaryportion of the cell gap adjusting film 103 and the transparent electrode602 is preferably larger than the distance d1 between the boundaryportion of the cell gap adjusting film 103 and the reflection electrode601. The distance d1′ between the boundary portion of the cell gapadjusting film 103 and the transparent electrode 602 is preferably 1.1to 7 μm. However, it is not limited to this.

Note that the reflection electrode 601 is not required to be providedover the lower layer 104. The reflection electrode 601 in the reflectionregion is provided only for reflecting light; therefore, it may beprovided in or below the lower layer 104.

In addition, a plurality of the reflection electrodes 601 may beprovided. For example, a part of the reflection electrodes 601 may beprovided over the lower layer 104, and another part of the reflectionelectrodes 601 may be provided in the lower layer 104.

The reflection electrode may be used also as an electrode which is usedfor another purpose. For example, the reflection electrode may be usedalso as an electrode for forming a storage capacitor.

Note that description in this embodiment mode is the description inEmbodiment Mode 1 a part of which is changed. Therefore, the descriptionin Embodiment Mode 1 can be applied to the description in thisembodiment mode.

Embodiment Mode 3

Although description is made of the case where the reflection electrodeis even in Embodiment Modes 1 and 2, it is not limited to this. When thereflection electrode is uneven, light is diffused; therefore, a wholeluminance is averaged and a clear image can be obtained in the case ofperforming a display of reflecting mode.

FIGS. 7A and 7B show an example of the case where the reflectionelectrode has an uneven portion. An upper surface of a cell gapadjusting film 703 has an uneven portion. As a result, a reflectionelectrode 701 which is formed over the cell gap adjusting film 703 hasan uneven portion. Note that it is not preferable that the unevenportion be too large because a large uneven portion affects a directionthat the liquid crystal is inclined. Therefore, a thickness d4 of aprojecting portion of the cell gap adjusting film 703 is preferablysmaller than the thickness d3 of the cell gap adjusting film 703. Forexample, the thickness d4 of the projecting portion of the cell gapadjusting film 703 is preferably 0.5 μm or less. However, it is notlimited to this.

In addition, the projecting portion of the cell gap adjusting film 703is preferably arranged approximately in parallel with the slit 105 (thegap, the space, or the like) of the electrode, the transparent electrode102, and the reflection electrode 701 as shown in FIG. 7A. By beingarranged approximately in parallel, disorder of orientation of theliquid crystal can be reduced, and light can be diffused.

Note that in the case where the thickness d4 of the projecting portionof the cell gap adjusting film 703 is small, the projecting portion ofthe cell gap adjusting film 703 may be arranged in random as shown inFIG. 8A. FIG. 8B is a cross sectional view taken a line A1-A1′ in FIG.8A.

The cell gap adjusting film 703 may have a stacked-layer structure. Forexample, the cell gap adjusting film 703 is formed by forming a flatportion, and an uneven portion over the flat portion.

Unevenness may be formed by forming an object over the cell gapadjusting film 703, and forming the reflection electrode 701 thereover.The object is not the cell gap adjusting film 703. For example, anuneven portion may be formed by forming the transparent electrode inaccordance with unevenness, and forming the reflection electrode 701thereover.

As shown in FIGS. 6A and 6B, in the case where the reflection electrodeis formed below the cell gap adjusting film, light can be diffused bymaking a surface of the reflection electrode uneven. This case is shownin FIGS. 9A and 9B. A lower layer 904 is provided with an unevenportion, over which a reflection electrode 901 is formed, over which acell gap adjusting film 903 is formed. The transparent electrode 602 isformed over the cell gap adjusting film 903. The transparent electrode602 is flat, so that orientation of the liquid crystal thereover is notdisturbed. By using this structure, light can be diffused withoutdisturbing orientation of the liquid crystal molecules.

For example, a thickness d5 of a projecting portion of the lower layer904 is preferably 1.0 μm or less. Therefore, light can be sufficientlydiffused. However, it is not limited to this.

In FIG. 9A, although a projecting portion of the lower layer 904 isarranged approximately in parallel with the slit 605 (the gap, thespace, or the like) of the electrode, the transparent electrode 102, thereflection electrode 901, and the transparent electrode 602, it is notlimited to this. The projecting portion of the reflection electrode 901may be arranged in random as shown in FIG. 10A. It is preferable to bearranged in random because a profound effect on light diffusion can beobtained. Note that FIGS. 9B and 10B are cross sectional views taken aline A3-A3′ in FIGS. 9A and 10B, respectively.

In the case where the lower layer 904 is provided with the unevenportion as in FIGS. 9A, 9B, 10A, and 10B, the projecting portion may beformed of a material containing an organic material. The materialcontaining an organic material preferably includes acrylic, polyimide,or polycarbonate, for example. Alternatively, a wire, an electrode, orthe like may be formed in accordance with the uneven portion, over whichan interlayer film may be formed by using a film with poor planarity.For example, a film containing silicon oxide or silicon nitride isprovided over a wire or an electrode, thereby the uneven portion of thelower layer 904 may be formed.

Note that description in this embodiment mode is the description inEmbodiment Modes 1 and 2 a part of which are changed or improved.Therefore, the description in Embodiment Modes 1 and 2 can be applied tothe description in this embodiment mode.

Embodiment Mode 4

The boundary portion between the reflection region and the transmissionregion is described in the aforementioned embodiment modes. In thisembodiment mode, each of the reflection region and the transmissionregion and the like are also described.

FIG. 11A is a top plan layout view. FIG. 11B is a cross sectional viewtaken along lines A4-A4′ and A5-A5′ in FIG. 11A. As shown in FIGS. 11Aand 11B, a slit (a gap, a space, or the like) of an electrode is formedin the reflection region and the transmission region. When a slit 1105 a(a gap, a space, or the like) of an electrode in the reflection regionis compared with a slit 1105 b (a gap, a space, or the like) of anelectrode in the transmission region, a width d6 of the slit 1105 a (thegap, the space, or the like) of the electrode in the reflection regionis preferably larger than a width d7 of the slit 1105 b (the gap, thespace, or the like) of the electrode in the transmission region. Asshown in FIG. 11B, liquid crystal molecules 1106 a and 1106 b arecontrolled by using the slit 1105 a (the gap, the space, or the like) ofthe electrode in the reflection region, while liquid crystal molecules1106 c and 1106 d are controlled by using the slit 1105 b (the gap, thespace, or the like) of the electrode in the transmission region. In thiscase, in the reflection region, a cell gap of the liquid crystal issmaller than that in the transmission region because of having the cellgap adjusting film 103; therefore, distortion of the electric field isnot enough unless the slit 1105 a (the gap, the space, or the like) ofthe electrode is made to be large. In addition, an electrode on anopposite side across the liquid crystal molecules is provided with anorientation film, thereby orientation of the liquid crystal molecules iscontrolled. When the cell gap of the liquid crystal is small, it becomesdifficult to move the liquid crystal molecules by supplying the electricfield because an effect of the orientation film of an electrode of anopposite side is large. For the aforementioned reasons, the width d6 ofthe slit 1105 a (the gap, the space, or the like) of the electrode inthe reflection region is preferably larger than the width d7 of the slit1105 b (the gap, the space, or the like) of the electrode in thetransmission region.

As shown in FIGS. 12A and 12B, when a width d8 of a slit 1205 a (a gap,a space, or the like) of an electrode in the boundary portion betweenthe reflection region and the transmission region is compared with thewidth d7 of the slit 1105 b (the gap, the space, or the like) of theelectrode in the transmission region, the width d8 is preferably largerthan the width d7. This is because the width d8 includes a function ofcontrolling the liquid crystal in the reflection region. The width d8 isrequired to be large in order to control the liquid crystalsufficiently. Note that FIG. 12A is a top plan layout view. FIG. 12B isa cross sectional view taken a line A6-A6′ in FIG. 12A.

As shown in FIGS. 13A and 13B, when the width d8 of the slit 1205 a (thegap, the space, or the like) of the electrode in the boundary portionbetween the reflection region and the transmission region is comparedwith the width d6 of the slit 1105 a (the gap, the space, or the like)of the electrode in the transmission region, the width d8 is preferablyalmost equal to the width d6. This is because both of the widths includecontrol of the liquid crystal in the reflection region. Note that FIG.13A is a top plan layout view. FIG. 13B is a cross sectional view takena line A7-A7′ in FIG. 13A.

For example, the width d8 of the slit 1205 a (the gap, the space, or thelike) of the electrode in the boundary portion between the reflectionregion and the transmission region is preferably 1.1 to 10.0 μm. Thewidth d6 of the slit 1105 a (the gap, the space, or the like) of theelectrode in the reflection region is preferably 1.1 to 10.0 μm. Thewidth d7 of the slit 1105 b (the gap, the space, or the like) of theelectrode in the transmission region is preferably 1.0 to 9.0 μm.However, they are not limited to these.

Note that description in this embodiment mode is the description inEmbodiment Modes 1 to 3 a part of which are changed, improved ordetailed. Therefore, the description in Embodiment Modes 1 to 3 can beapplied to the description in this embodiment mode.

Embodiment Mode 5

The liquid crystal molecules 106 described in FIGS. 1A and 1B areinclined in one direction. However, in the case where the liquid crystalmolecules in one pixel are inclined only in one direction, a viewingangle is narrow. That is, the way the liquid crystal looks is changedwhen seen from a certain direction because the direction that the liquidcrystal molecules are inclined looks different depending on a viewpoint.

The liquid crystal molecules are not preferably inclined in only onedirection, but they are preferably inclined in various directions. Thatis, it is preferable to employ a multi-domain structure and have aplurality of regions so as to provide a plurality of directions that theliquid crystal molecules are inclined. For example, in the case wherethe liquid crystal is inclined in a certain direction, a region wherethe liquid crystal is inclined in an opposite direction is preferablyformed.

A projection (a protruding portion) or a slit (a gap, a space, or thelike) can be provided on an electrode portion so that the liquid crystalis inclined in the opposite direction.

FIGS. 14A and 14B are configuration diagrams in the case where theliquid crystal is inclined in right side and in the case where theliquid crystal is inclined in left side in portions adjacent to the cellgap adjusting film 103. Note that FIG. 14A is a top plan layout view.FIG. 14B is a cross sectional view taken a line A8-A8′ in FIG. 14A. Byproviding slits 1405 a and 1405 b (a gap, a space, or the like) of anelectrode in parallel on both sides of the reflection electrode 101,each liquid crystal molecules are inclined in opposite directions eachother like the liquid crystal molecules 1406 a and 1406 b. Consequently,the ways the liquid crystal molecules look can be averaged; therefore, aviewing angle can be increased.

Note that in FIGS. 14A and 14B, although a plane on which the liquidcrystal is inclined is on the same plane as A8-A8′, it is not limited tothis. As shown in FIGS. 15A, 15B, 15C and 15D, a cross section A9-A9′and a cross section A10-A10′ may be arranged perpendicular to eachother, which can increase a viewing angle. Note that FIGS. 15A and 15Bare top plan layout views. FIG. 15C is a cross sectional view taken aline A9-A9′ in FIG. 15A. FIG. 15D is a cross sectional view taken a lineA10-A10′ in FIG. 15C.

In addition, FIGS. 15A, 15B, 15C and 15D and FIGS. 14A and 14B may becombined. That is, the liquid crystal molecules may be set to move ondifferent planes like the cross section A9-A9′ and the cross sectionA10-A10′, and the liquid crystal molecules on the same plane may be setto be inclined in various directions like a cross section A8-A8′.

In the case where the liquid crystal molecules are inclined and in aradial pattern from one point as a flower blooms, a region in which mostof the liquid crystal molecules inclined to various directions is madeat a boundary with another adjacent region; therefore, disorder oforientation of the liquid crystal molecules may occur. However, in theinvention, the liquid crystal is aligned in a region extended inparallel; therefore, disorder of orientation of the liquid crystalmolecules hardly occurs.

Note that description in this embodiment mode is the description inEmbodiment Modes 1 to 4 a part of which are changed, improved ordetailed. Therefore, the description in Embodiment Modes 1 to 4 can beapplied to the description in this embodiment mode.

Embodiment Mode 6

An electrode on one side is described in the aforementioned embodimentmodes. Actually, an electrode and a substrate are provided on anopposite side, across the liquid crystal. A projection on an electrodeportion, a slit (a gap, a space, or the like) of an electrode, and thelike are required to be provided on this opposite substrate in orderthat the liquid crystal molecules are easily inclined.

FIGS. 16A and 16B show an example in which a slit 1605 (a gap, a space,or the like) of an electrode is provided over an opposite substrate1604. FIG. 16A is a top plan layout view. FIG. 16B is a cross sectionalview taken a line A11-A11′ in FIG. 16A. As shown in FIG. 16B,transparent electrodes 1601 and 1602 and the like are provided over theopposite substrate 1604, which is not required to reflect light. Theslit 1605 (the gap, the space, or the like) of the electrode on theopposite substrate 1604 is preferably arranged approximately in themiddle of the reflection electrode 101 and the transparent electrodes.Therefore, liquid crystal molecules 1606 which are inclined in eachdirection are arranged evenly.

In addition, as shown in FIG. 16A that is a plan view, the slit 1605(the gap, the space, or the like) of the electrode on the oppositesubstrate 1604 and the transparent electrodes 1601 and 1602 on theopposite substrate are arranged approximately in parallel with the slit105 (the gap, the space, or the like) of the electrode, the transparentelectrode 102, and the reflection electrode 101. Therefore, disorder oforientation of the liquid crystal can be reduced because the directionthat the liquid crystal is inclined can be controlled appropriately byboth substrates between which the liquid crystal is sandwiched.

Next, FIGS. 17A and 17B show the case where a projection 1705 isprovided on the opposite substrate 1604. FIG. 17A is a top plan layoutview. FIG. 17B is a cross sectional view taken a line A11-A11′ in FIG.17A. As shown in FIG. 17B that is a cross sectional view, a transparentelectrode 1701 is provided to cover the projection 1705. However, it isnot limited to this. The transparent electrode may be provided betweenthe projection 1705 and the opposite substrate 1604. An orientation filmis provided at a portion in contact with the liquid crystal molecules.Therefore, in the case of FIG. 17B, the orientation film is provided tocover the transparent electrode 1701. The projection 1705 on theopposite substrate 1604 is preferably arranged approximately in themiddle of the reflection electrode 101 and the transparent electrodes.Therefore, liquid crystal molecules 1706 which are inclined in eachdirection are arranged evenly.

In addition, as shown in FIG. 17A that is a plan view, the projection1705 over the opposite substrate 1604 is arranged approximately inparallel with the slit 105 (the gap, the space, or the like) of theelectrode, the transparent electrode 102, and the reflection electrode101. Therefore, disorder of orientation of the liquid crystal can bereduced because the direction that the liquid crystal is inclined can becontrolled appropriately by both substrates between which the liquidcrystal is sandwiched.

Next, description is made of a width of the slit (the gap, the space, orthe like) of the electrode with reference to a cross sectional viewshown in FIG. 18. In FIG. 18, when a width d10 of a slit 1805 b (a gap,a space, or the like) of the transparent electrode on the oppositesubstrate 1604 in the reflection region is compared with a width d9 of aslit 1805 a (a gap, a space, or the like) of the transparent electrodeon the opposite substrate 1604 in the transmission region, the width d9is preferably smaller than the width d10. The relation between the widthd9 and the width d10 is similar to the relation between the width d6 ofthe slit 1105 a (the gap, the space, or the like) of the electrode inthe reflection region and the width d7 of the slit 1105 b (the gap, thespace, or the like) of the electrode in the transmission region.

A cell gap of the liquid crystal in the reflection region is smallerthan that in the transmission region because of having the cell gapadjusting film 103; therefore, distortion of the electric field is notenough unless the slit 1805 b (the gap, the space, or the like) of theelectrode is made to be large. Consequently, the width d10 of the slit1805 b (the gap, the space, or the like) of the electrode in thereflection region is preferably larger than the width d9 of the slit1805 a (the gap, the space, or the like) of the electrode in thetransmission region.

In addition, the width d6 of the slit 1105 a (the gap, the space, or thelike) of the electrode in the reflection region shown in FIGS. 13A and13B is preferably approximately equal to the width d10 of the slit 1805b (the gap, the space, or the like) of the electrode on the oppositesubstrate 1604 in the reflection region shown in FIG. 18. This isbecause if the width d6 and the width d10 are the same, a symmetryproperty is improved and the liquid crystal is arranged evenly;therefore, an orientation defect of the liquid crystal can be reduced.

Similarly, the width d7 of the slit 1205 b (the gap, the space, or thelike) of the electrode in the transmission region shown in FIGS. 12A and12B is preferably approximately equal to the width d9 of the slit 1805 a(the gap, the space, or the like) of the electrode in the transmissionregion shown in FIG. 18. This is because if the width d6 and the widthd9 are the same, a symmetry property is improved and the liquid crystalis arranged evenly; therefore, an orientation defect of the liquidcrystal can be reduced.

Next, description is made of a width of a projection of an electrodeportion with reference to a cross sectional view shown in FIG. 19. InFIG. 19, when a width d12 of a projection 1905 b on the oppositesubstrate 1604 in the reflection region is compared with a width d11 ofa projection 1905 a on the opposite substrate 1604 in the transmissionregion, the width d11 is preferably smaller than the width d12. Therelation between the width d11 and the width d12 is similar to therelation between the width d6 of the slit 1105 a (the gap, the space, orthe like) of the electrode in the reflection region and the width d7 ofthe slit 1105 b (the gap, the space, or the like) of the electrode inthe transmission region.

A cell gap of the liquid crystal in the reflection region is smallerthan that in the transmission region because of having the cell gapadjusting film 103; therefore, distortion of the electric field is notenough unless the projection 1905 b is made to be larger. Consequently,the width d12 of the projection 1905 b in the reflection region ispreferably larger than the width d11 of the projection 1905 a in thetransmission region.

In addition, the width d6 of the slit 1105 a (the gap, the space, or thelike) of the electrode in the reflection region shown in FIGS. 13A and13B is preferably approximately the same as the width d12 of theprojection 1905 b on the opposite substrate 1604 in the reflectionregion. This is because if the width d6 and the width d12 are the same,a symmetry property is improved and the liquid crystal is arrangedevenly; therefore, an orientation defect of the liquid crystal can bereduced.

Similarly, the width d7 of the slit 1205 b (the gap, the space, or thelike) of the electrode in the reflection region shown in FIGS. 12A and12B is preferably approximately equal to the width d11 of the projection1905 a on the opposite substrate 1604 in the transmission region shownin FIG. 18. This is because if the width d7 and the width d11 are thesame, a symmetry property is improved and the liquid crystal is arrangedevenly; therefore, an orientation defect of the liquid crystal can bereduced.

In addition, the opposite substrate 1604 may have unevenness. Light isreflected diffusely by the unevenness; therefore, whole luminance isaveraged and a clear image can be obtained. That is, a liquid crystaldisplay device with certain brightness can be obtained when seen fromany direction. As a result, light reaches a viewer of a display well,and luminance is increased substantially.

In addition, the opposite substrate 1604 is provided with the cell gapadjusting film. A film thickness can be adjusted easily by providing thecell gap adjusting films on both sides between which the liquid crystalis sandwiched in order to make a thickness of the cell gap adjustingfilm thicker. Note that the cell gap adjusting film which is providedover the opposite substrate 1604 can have unevenness as shown inEmbodiment Mode 3.

Note that description in this embodiment mode can commonly used for thedescription in Embodiment Modes 1 to 5. Therefore, the description inEmbodiment Modes 1 to 5 can be combined with the description in thisembodiment mode.

Embodiment Mode 7

FIG. 20 shows a top plan layout view in the case where a transistor andvarious wires are provided over the above-described lower layer 104.Note that FIG. 20 shows the case where a bottom gate transistor isemployed as a transistor. A gate signal line 2001 and a capacitor line2002 which are formed of the same material in the same layer areprovided in a lateral direction. A part of the gate signal line 2001functions as a gate electrode of the transistor. A part of the capacitorline 2002 functions as an electrode of a storage capacitor. A gateinsulating film is formed to cover a whole area. Note that the gateinsulating film is not shown in FIG. 20 because FIG. 20 is a plan layoutview.

Silicon 2003 is formed over the gate insulating film. This portionfunctions as a transistor, over which a source signal line 2004, a drainelectrode 2005 and a reflection electrode 2006 which are formed of thesame material in the same layer are provided. A storage capacitor isformed between the reflection electrode 2006 and the capacitor line2002. Note that as an electrode of the storage capacitor, a pixelelectrode 2007 may be employed instead of the reflection electrode 2006.An interlayer insulating film is formed to cover a whole area over thesource signal line 2004, the drain signal line 2005 and the reflectionelectrode 2006. The interlayer insulating film is not described in FIG.20 because FIG. 20 is a top plan layout view. Contact holes 2008 and2009 are provided in the interlayer insulating film. A cell gapadjusting film 2010 is formed over the interlayer insulating film in thereflection region, over which a transparent conductive film 2011 isformed.

In the layout view shown in FIG. 20, the cell gap adjusting film 2010 isformed over the reflection electrode 2006; therefore, the case of FIGS.6A and 6B is used here. In addition, the storage capacitor is providedin the reflection region; therefore, an area of the transmission regioncan be made large.

As shown in the layout view of FIG. 20, a region where a slit (a gap, aspace, or the like) of an electrode and a boundary of the cell gapadjusting film 2010 are provided in parallel is formed; therefore,orientation of the liquid crystal is performed appropriately. Inaddition, a region where the transparent conductive film 2011 and theboundary of the cell gap adjusting film 2010 are provided in parallel isformed; therefore, orientation of the liquid crystal is performedappropriately.

The cell gap adjusting film 2010, the electrode, the slit, and the likeare provided similarly to those shown in FIGS. 14A, 14B, 15A, 15B, 15Cand 15D; therefore, a viewing angle can be increased.

FIG. 21 shows a cross sectional view taken a line B1-B1′ in FIG. 20. Thestorage capacitor is provided in the reflection region as shown in FIG.21. Two electrodes of the storage capacitor are used also as thereflection electrode. Note that the gate insulating film and theinterlayer insulating film, which are not shown in FIG. 20, aredescribed as a gate insulating film 2101 and an interlayer insulatingfilm 2102 in FIG. 21.

Next, FIG. 22 shows a layout view in the case of a top gate transistor.Silicon 2203 is provided, over which a gate insulating film 2301 isformed to cover a whole area. The gate insulating film 2301 is notdescribed in FIG. 22 because FIG. 22 is a top plan layout view. A gatesignal line 2201 and a capacitor line 2202 which are formed of the samematerial in the same layer are provided in a lateral direction over thegate insulating film 2301. A part of the gate signal line 2201 which isformed over the silicon 2203 functions as a gate electrode of thetransistor. A part of the capacitor line 2202 functions as an electrodeof the storage capacitor. An interlayer insulating film 2302 is formedthereover to cover a whole area. The interlayer insulating film 2302 isnot described in FIG. 22 because FIG. 22 is a plan layout view. A sourcesignal line 2204, a drain signal line 2205 and a reflection electrode2206 which are formed of the same material in the same layer are formedover the interlayer insulating film 2302. The storage capacitor isformed between the reflection electrode 2206 and the capacitor line2202. Note that as the electrode of the storage capacitor, an electrodein the same layer as the silicon 2203 may be used, and the storagecapacitor may be formed between the electrode and the capacitor line2002. An interlayer insulating film 2303 is formed thereover to cover awhole area. The interlayer insulating film 2303 is not described in FIG.22 because FIG. 22 is a top plan layout view. A cell gap adjusting film2210 is formed over the interlayer insulating film 2303 in thereflection region, over which a transparent conductive film 2211 isformed.

In the layout view shown in FIG. 22, the cell gap adjusting film 2210 isformed over the reflection electrode 2206; therefore, the case of FIGS.6A and 6B is used here.

In addition, the storage capacitor is provided in the reflection region;therefore, an area of the transmission region can be made large. Asshown in this layout view, a region where a slit (a gap, a space, or thelike) of an electrode and a boundary of the cell gap adjusting film 2210are provided in parallel is provided; therefore, orientation of theliquid crystal is performed appropriately. In addition, a region wherethe transparent conductive film 2211 and the boundary of the cell gapadjusting film 2210 are provided in parallel is provided; therefore,orientation of the liquid crystal is performed appropriately.

The cell gap adjusting film, the electrode, the slit, and the like areprovided similarly to those shown in FIGS. 14A, 14B, 15A, 15B, 15C and15D; therefore, a viewing angle can be increased.

FIG. 23 shows a cross sectional view taken a line B2-B2′ in FIG. 22. Thestorage capacitor is provided in the reflection region as shown in FIG.23. Two electrodes of the storage capacitor are used also as thereflection electrode.

Note that description in this embodiment mode can commonly used for thedescription in Embodiment Modes 1 to 6. Therefore, the description inEmbodiment Modes 1 to 6 can be combined with the description in thisembodiment mode.

Embodiment Mode 8

FIGS. 20 and 22 show examples of the layout views of the transparentelectrode and the reflection electrode. Next, some examples of theelectrode is described.

FIG. 24 shows an example of a layout view of an electrode. In over anelectrode 2411, slits 2405 (a gap, a space, or the like) of an electrodeare provided in two oblique directions. Reference numerals 2403 a, 2403b, and 2403 c correspond to boundary portions of the cell gap adjustingfilms. The cell gap adjusting film is provided in a portion enclosed bya dotted line. A large part of this boundary is arranged approximatelyin parallel with the slits 2405 (the gap, the space, or the like) of theelectrode. Therefore, an orientation defect of the liquid crystal can bereduced.

One or a plurality of the cell gap adjusting films can be provided. Thatis, only the cell gap adjusting film 2403 a may be provided, or twofilms of the cell gap adjusting film 2403 b and the cell gap adjustingfilm 2403 c may be provided. Alternatively, all of the cell gapadjusting films 2403 a, 2403 b, and 2403 c may be provided. The cell gapadjusting film 2403 a has two directions of slits, which are anobliquely upper right direction and an obliquely upper left direction.Therefore, a viewing angle can be increased due to a plurality ofdirections that the liquid crystal molecules are inclined. Similarly,when two films of the cell gap adjusting film 2403 b and the cell gapadjusting film 2403 c are employed, a viewing angle can be increasedbecause of a plurality of directions that the liquid crystal moleculesare inclined.

A portion where the cell gap adjusting film exists serves as thereflection region, and the reflection electrode is formed in thereflection region. An electrode 2411 in the portion where the cell gapadjusting film exists may become the reflection electrode.Alternatively, the reflection electrode may be provided below the cellgap adjusting film as shown in FIGS. 21 and 23. A portion where the cellgap adjusting film does not exist becomes the transmission region. Thereflection electrode and the transparent electrode are both in the casewhere they are electrically connected as one electrode as shown in FIGS.2A to 2C and in the case where they are different electrodes as shown inFIGS. 6A and 6B.

Another example of the electrode is shown in FIG. 25. In an electrode2511, slits 2505 (a gap, a space, or the like) of an electrode isprovided in two oblique directions. A reference numeral 2503 correspondsto the boundary portion of the cell gap adjusting film. The cell gapadjusting film is provided in a portion enclosed by a dotted line. Alarge part of this boundary is arranged approximately in parallel withthe slits 2505 (the gap, the space, or the like) of the electrode.Therefore, an orientation defect of the liquid crystal can be reduced.

In addition, the slits 2505 (the gap, the space, or the like) of theelectrode is long and not being cut as shown in FIG. 24. Therefore, anorientation defect of the liquid crystal can be reduced.

Note that a portion where the cell gap adjusting film exists serves asthe reflection region, and the reflection electrode is formed in thereflection region. The electrode 2511 in the portion where the cell gapadjusting film exists may serve as the reflection electrode.Alternatively, the reflection electrode may be provided below the cellgap adjusting film as shown in FIGS. 21 and 23. A portion where the cellgap adjusting film does not exist becomes the transmission region. Thereflection electrode and the transparent electrode are both in the casewhere they are electrically connected as one electrode as shown in FIGS.2A to 2C and in the case where they are different electrodes as shown inFIGS. 6A and 6B.

Another example of the electrode is shown in FIG. 26. A slit 2605 (agap, a space, or the like) of an electrode is provided at an electrode2611. The slit has a shape of teeth of a comb. Cell gap adjusting films2603 a and 2603 b may be provided along an envelope like passing a tipof the shape of teeth of a comb. Note that the cell gap adjusting films2603 a and 2603 b may be provided along the shape of teeth of a comb.The cell gap adjusting film is provided in a portion enclosed by adotted line of the cell gap adjusting films 2603 a and 2603 b. A largepart of this boundary is arranged approximately in parallel with theslit 2605 (the gap, the space, or the like) of the electrode or theenvelope. Therefore, an orientation defect of the liquid crystal can bereduced.

A portion where the cell gap adjusting film exists becomes thereflection region, and the reflection electrode is formed in thereflection region. An electrode 2611 in the portion where the cell gapadjusting film exists may become the reflection electrode.Alternatively, the reflection electrode may be provided below the cellgap adjusting film as shown in FIGS. 21 and 23. A portion where the cellgap adjusting film does not exist becomes the transmission region. Thereflection electrode and the transparent electrode are both in the casewhere they are electrically connected as one electrode as shown in FIGS.2A to 2C and in the case where they are different electrodes as shown inFIGS. 6A and 6B.

Another example of the electrode is shown in FIG. 27. In an electrode2711, slits 2705 (a gap, a space, or the like) of an electrode has adogleg shape and is provided in two oblique directions. Referencenumerals 2703 a and 2703 b correspond to the boundary portions of thecell gap adjusting film. The cell gap adjusting film is provided in aportion enclosed by a dotted line. A large part of this boundary isarranged approximately in parallel with the slits 2705 (the gap, thespace, or the like) of the electrode. Therefore, an orientation defectof the liquid crystal can be reduced.

One or a plurality of the cell gap adjusting films can be provided. Thatis, only the cell gap adjusting film 2703 a or the cell gap adjustingfilm 2703 b may be provided, or two films of the cell gap adjusting film2703 a and the cell gap adjusting film 2703 b may be provided. When thecell gap adjusting film 2703 a and the cell gap adjusting film 2703 bare employed, a viewing angle can be increased because of a plurality ofdirections that the liquid crystal molecules are inclined.

A portion where the cell gap adjusting film exists serves as thereflection region, and the reflection electrode is formed in thereflection region. The electrode 2711 in the portion where the cell gapadjusting film exists may serve as the reflection electrode.Alternatively, the reflection electrode may be provided below the cellgap adjusting film as shown in FIGS. 21 and 23. A portion where the cellgap adjusting film does not exist becomes the transmission region. Thereflection electrode and the transparent electrode are both in the casewhere they are electrically connected as one electrode as shown in FIGS.2A to 2C and in the case where they are different electrodes as shown inFIGS. 6A and 6B.

Another example of the electrode is shown in FIG. 28. In an electrode2811, slits 2805 (a gap, a space, or the like) of an electrode isprovided in two oblique directions. The electrode 2811 is provided likea branch growing from a trunk. A reference numeral 2803 corresponds tothe boundary portion of the cell gap adjusting film. The cell gapadjusting film is provided in a portion enclosed by a dotted line. Alarge part of this boundary is arranged approximately in parallel withthe electrode 2811. Therefore, an orientation defect of the liquidcrystal can be reduced.

A portion where the cell gap adjusting film exists serves as thereflection region, and the reflection electrode is formed in thereflection region. The electrode 2811 in the portion where the cell gapadjusting film exists may serve as the reflection electrode.Alternatively, the reflection electrode may be provided below the cellgap adjusting film as shown in FIGS. 21 and 23. A portion where the cellgap adjusting film does not exist becomes the transmission region. Thereflection electrode and the transparent electrode are both in the casewhere they are electrically connected as one electrode as shown in FIGS.2A to 2C and in the case where they are different electrodes as shown inFIGS. 6A and 6B.

Note that a layout view of the electrode is not limited to thosedescribed in this embodiment mode.

Note that description in this embodiment mode can commonly used for thedescription in Embodiment Modes 1 to 7. Therefore, the description inEmbodiment Modes 1 to 7 can be combined with the description in thisembodiment mode.

Embodiment Mode 9

FIGS. 21 and 23 show cross-sectional structural views in the case ofemploying the bottom gate transistor and the case of employing the topgate transistor. In this embodiment mode, another cross-sectionalstructural view is described. Note that a cross-sectional structure isnot limited to those described in this embodiment mode.

FIG. 29 shows an example of a cross sectional view in the case ofemploying the bottom gate transistor. A gate signal line 2901 and acapacitor line 2902 are formed of the same material in the same layer. Apart of the gate signal line 2901 functions as a gate electrode of thetransistor. A part of the capacitor line 2902 functions as an electrodeof the storage capacitor. A gate insulating film 2991 is formedthereover. Silicon 2903 is formed over the gate insulating film 2991.This portion functions as the transistor. A source signal line 2904 anda drain signal line 2905 are formed over the silicon 2903. A capacitorelectrode 2906 is formed of the same material in the same layer as thesource signal line 2904 and the drain signal line 2905. The storagecapacitor is formed between the capacitor electrode 2906 and thecapacitor line 2902. An interlayer insulating film 2992 is formed overthe source signal line 2904, the drain signal line 2905, and thecapacitor electrode 2906, over which a cell gap adjusting film 2910 isformed.

In the structure shown in FIG. 29, the cell gap adjusting film 2910 iseliminated at least from the transmission region. The cell gap adjustingfilm 2910 may be eliminated from a region other than the reflectionregion. A reflection electrode 2913 is formed over the cell gapadjusting film 2910. Note that a contact electrode 2912 is not requiredto be provided. A transparent electrode 2911 is formed over thereflection electrode 2913. By providing the transparent electrode 2911over the reflection electrode 2913, the transparent electrode 2911 andthe reflection electrode 2913 are electrically connected.

As the electrode of the storage capacitor, the transparent electrode2911 and the reflection electrode 2913 may be employed instead of thecapacitor electrode 2906. At that time, a thick material is preferablyeliminated because an insulating film between the electrodes ispreferably as thin as possible in order to make a capacitance valuelarge.

In FIG. 29, although the transparent electrode 2911 is formed over thereflection electrode 2913, it is not limited to this. The reflectionelectrode 2913 may be formed over the transmission region 2911.

Although the interlayer insulating film 2992 is formed over the sourcesignal line 2904, the drain signal line 2905, and the capacitorelectrode 2906, it is not limited to this. If circumstances require, theinterlayer insulating film 2992 is provided.

Note that in FIG. 29, although the reflection electrode 2913 isprovided, it is not limited to this. The reflection electrode may beformed by sharing the drain electrode 2905, an electrode or a wire inthe same layer thereof, the capacitor line 2902, or an electrode or awire in the same layer thereof, or by forming a new electrode.

Next, in the case where the reflection electrode with unevenness isformed below the cell gap adjusting film as shown in FIGS. 9A and 9B,FIG. 30 shows an example of a cross sectional view in the case ofemploying the bottom gate transistor A gate signal line 3001 and acapacitor line 3002 are formed of the same material in the same layer. Apart of the gate signal line 3001 functions as a gate electrode of thetransistor. A part of the capacitor line 3002 functions as an electrodeof the storage capacitor. A gate insulating film 3091 is formedthereover. Silicon 3003 is formed over the gate insulating film 3091.This portion functions as the transistor. A source signal line 3004 anda drain signal line 3005 are formed over the silicon 3003. A capacitorelectrode 3006 is formed of the same material in the same layer as thesource signal line 3004 and the drain signal line 3005. The storagecapacitor is formed between the capacitor electrode 3006 and thecapacitor line 3002. An interlayer insulating film 3092 is formed overthe source signal line 3004, the drain signal line 3005, and thecapacitor electrode 3006.

A plurality of contact holes are provided in the interlayer insulatingfilm 3092. A reflection electrode 3013 can have unevenness by using thecontact holes. The reflection electrode 3013 and a connection electrode3012 are formed over the interlayer insulating film 3092 having thecontact holes.

A cell gap adjusting film 3010 is formed over the reflection electrode3013 and the connection electrode 3012. Note that the cell gap adjustingfilm 3010 is eliminated at least from the transmission region. The cellgap adjusting film 3010 may be eliminated from a region other than thereflection region. A transparent electrode 3011 is formed over the cellgap adjusting film 3010. In order to be electrically connected to thetransparent electrode 3011, a part of the reflection electrode 3013 isformed outside of the cell gap adjusting film 3010, at which it isconnected to the transparent electrode 3011.

As the electrode of the storage capacitor, the transparent electrode3011 and the reflection electrode 3013 may be employed instead of thecapacitor electrode 3006. At that time, a thick material is preferablyeliminated because an insulating film between the electrodes ispreferably as thin as possible in order to make a capacitance valuelarge.

In FIG. 30, although the reflection electrode 3013 is provided, it isnot limited to this. The reflection electrode may be formed by sharingthe drain electrode 3005, an electrode or a wire in the same layerthereof, the capacitor line 3002, or an electrode or a wire in the samelayer thereof, or by forming a new electrode.

Next, in the case where the reflection electrode with unevenness isformed over the cell gap adjusting film as shown in FIGS. 7A and 7B,FIG. 31 shows an example of a cross sectional view in the case ofemploying the bottom gate transistor.

A gate signal line 3101 and a capacitor line 3102 are formed of the samematerial in the same layer. A part of the gate signal line 3101functions as a gate electrode of the transistor. A part of the capacitorline 3102 functions as an electrode of the storage capacitor A gateinsulating film 3191 is formed thereover. Silicon 3103 is formed overthe gate insulating film 3191. This portion functions as the transistor.

A source signal line 3104 and a drain signal line 3105 are formed overthe silicon 3103. A capacitor electrode 3106 is formed of the samematerial in the same layer as the source signal line 3104 and the drainsignal line 3105. The storage capacitor is formed between the capacitorelectrode 3106 and the capacitor line 3102. An interlayer insulatingfilm 3192 is formed over the source signal line 3104, the drain signalline 3105, and the capacitor electrode 3106, over which a cell gapadjusting film 3110 is formed. Note that the cell gap adjusting film3110 is eliminated at least from the transmission region. Note that thecell gap adjusting film 3110 may be eliminated from a region other thanthe reflection region.

A transparent electrode 3011 is formed over the cell gap adjusting film3110. The transparent electrode 3011 is formed in the reflection regionin order to be electrically connected to a reflection electrode 3112. Aprojection portion 3193 is formed thereover. Note that the projectionportion 3193 may be formed below the transparent electrode 3011. Thereflection electrode 3112 is formed subsequently.

A transparent electrode 3011 is provided below a reflection electrode3112, thereby being electrically connected to the reflection electrode3112.

As the electrode of the storage capacitor, the transparent electrode3011 and the reflection electrode 3112 may be employed instead of thecapacitor electrode 3106. At that time, a thick material is preferablyeliminated because an insulating film between the electrodes ispreferably as thin as possible in order to make a capacitance valuelarge.

In FIG. 31, although the reflection electrode 3112 is formed over thetransparent electrode 3011, it is not limited to this. The transparentelectrode 3011 may be formed over the reflection electrode 3112.

Although the interlayer insulating film 3192 is formed over the sourcesignal line 3104, the drain signal line 3105, and the capacitorelectrode 3106, it is not limited to this. If circumstances require, theinterlayer insulating film 3192 is provided.

Note that in this embodiment mode, although description is made of achannel etch type transistor as the bottom gate transistor, it is notlimited to this. A channel protective type (channel stop type)transistor of which a protective film is formed at an upper portion of achannel may be employed.

Next, FIG. 32 shows an example of a cross sectional view in the case ofemploying the top gate transistor.

Silicon 3203 is provided, over which a gate insulating film 3291 isformed. A gate signal line 3201 and a capacitor line 3202 are formed ofthe same material in the same layer over the gate insulating film 3291.A part of the gate signal line 3201 provided over the silicon 3203functions as a gate electrode of the transistor. A part of the capacitorline 3202 functions as an electrode of the storage capacitor. Aninterlayer insulating film 3292 is formed thereover. A source signalline 3204, a drain signal line 3205, and a capacitor electrode 3206 areformed of the same material in the same layer over the interlayerinsulating film 3292. The storage capacitor is formed between thecapacitor electrode 3206 and the capacitor line 3202. Note that as theelectrode of the storage capacitor, an electrode in the same layer asthe silicon 3203 may be used, and the storage capacitor may be formedbetween the electrode and the capacitor line 3202. A cell gap adjustingfilm 3210 is formed thereover. Note that the cell gap adjusting film3210 is eliminated at least from the transmission region. The cell gapadjusting film 3210 may be eliminated from a region other than thereflection region.

A transparent electrode 3211 is formed over the cell gap adjusting film3210. The transparent electrode 3211 is formed in the reflection regionin order to be electrically connected to a reflection electrode 3213.The reflection electrode 3213 is formed over the transparent electrode3211.

The transparent electrode 3211 is provided below the reflectionelectrode 3213, thereby being electrically connected to the reflectionelectrode 3113.

As the electrode of the storage capacitor, the transparent electrode3211 and the reflection electrode 3213 may be employed instead of thecapacitor electrode 3206. At that time, a thick material is preferablyeliminated because an insulating film between the electrodes ispreferably as thin as possible in order to make a capacitance valuelarge.

Note that in FIG. 32, although the reflection electrode 3213 is formedover the transparent electrode 3211, it is not limited to this. Thetransparent electrode 3211 may be formed over the reflection electrode3213.

Next, in the case where the reflection electrode with unevenness isformed below the cell gap adjusting film as shown in FIGS. 9A and 9B,FIG. 33 shows an example of a cross sectional view in the case ofemploying the top gate transistor.

Silicon 3303 is provided, over which a gate insulating film 3391 isformed. A gate signal line 3301 and a capacitor line 3302 are formed ofthe same material in the same layer over the gate insulating film 3391.A part of the gate signal line 3301, which is provided over the silicon3303, functions as a gate electrode of the transistor. A part of thecapacitor line 3302 functions as an electrode of the storage capacitor.An interlayer insulating film 3392 is formed thereover. A source signalline 3304, a drain signal line 3305, and a capacitor electrode 3306 areformed of the same material in the same layer over the gate insulatingfilm 3392. The storage capacitor is formed between the capacitorelectrode 3306 and the capacitor line 3302. Note that as the electrodeof the storage capacitor, an electrode in the same layer as the silicon2203 may be used, and the storage capacitor may be formed between theelectrode and the capacitor line 3302.

An interlayer insulating film 3393 is formed over the source signal line3304, the drain signal line 3305, the capacitor electrode 3306, and thelike. A plurality of contact holes are provided in the interlayerinsulating film 3393. A reflection electrode 3313 can have unevenness byusing the contact holes. The reflection electrode 3313 and a connectionelectrode 3214 are formed over the interlayer insulating film 3393having the contact holes.

A cell gap adjusting film 3310 is formed over the reflection electrode3213 and the connection electrode 3314. Note that the cell gap adjustingfilm 3310 is eliminated at least from the transmission region. The cellgap adjusting film 3310 may be eliminated from a region other than thereflection region.

A transparent electrode 3311 is formed over the cell gap adjusting film3310. In order to be electrically connected to the transparent electrode3311, a part of the reflection electrode 3313 is formed outside of thecell gap adjusting film 3310, at which it is connected to thetransparent electrode 3311.

Note that as the electrode of the storage capacitor, the transparentelectrode 3311 and the reflection electrode 3313 may be employed insteadof the capacitor electrode 3306. At that time, a thick material ispreferably eliminated because an insulating film between the electrodesis preferably as thin as possible in order to make a capacitance valuelarge.

Note that in FIG. 33, although the reflection electrode 3313 isprovided, it is not limited to this. The reflection electrode may beformed by sharing the drain electrode 3305, an electrode or a wire inthe same layer thereof, the capacitor line 3302, or an electrode or awire in the same layer thereof, or by forming a new electrode.

In this invention, various kinds of transistors can be applied such as athin film transistor (TFT) using a non-monocrystalline semiconductorfilm typified by amorphous silicon or polycrystalline silicon, a MOStransistor which is formed by using a semiconductor substrate or an SOIsubstrate, a junction type transistor, a bipolar transistor, atransistor using an organic semiconductor or a carbon nanotube, or othertransistors. In addition, a substrate over which a transistor isprovided is not limited, and a monocrystalline substrate, an SOIsubstrate, a grass substrate, or the like can be employed.

Note that the thin film transistor is preferably used for a transistorwhich is employed in this invention. As using the thin film transistor,a grass substrate, which is inexpensive and transparent, can be used asa substrate.

Note that in the specification, a semiconductor device is a deviceincluding a circuit which has a semiconductor element (a transistor, adiode, or the like). A light emitting device is a device including acircuit which has a light emitting element (an organic EL element, anelement used for FED, or the like). A display device is a deviceincluding a circuit which has a display element (an organic EL element,a liquid crystal element, a DMD, or the like).

Note that cross-sectional structures described in this specification areonly examples, and it is not limited to these. Various structures can beobtained by combining the description in Embodiment modes 1 to 8 freely.Description in this embodiment mode is a part of these combinations, andfurther, various combinations can be realized.

Embodiment Mode 10

A substrate over which the cell gap adjusting film is formed and anopposite substrate between which the liquid crystal is sandwiched arerequired to be maintained with a certain cell gap. Therefore, a spaceris required to be provided.

In that case, a method by which spacers of bead shape (spherical shape)are spread over a whole substrate and the liquid crystal is injected isused in general. However, in the case of the semi-transmission typeliquid crystal including the vertically aligned liquid crystal in theinvention, the spacers of bead shape (spherical shape) cannot maintain acell gap well because cell gaps are different in the transmission regionand in the reflection region.

Therefore, as shown in FIGS. 34 and 35, a spacer 3401 and a spacer 3501are preferably formed over the cell gap adjusting film 103 or a filmwhich is formed of the same layer as the cell gap adjusting film 103. Inthat case, the spacer 3401 and the spacer 3501 contribute to incliningthe liquid crystal molecules in a specific direction. Therefore, a slit(a gap, a space, or the like) of an electrode and the projection 1905 aare preferably not provided near the spacer 3401 and the spacer 3501.

The spacer 3401 and the spacer 3501 are required to be thick films;therefore, preferably formed of a material containing an organicmaterial. The material containing an organic material preferablyincludes acrylic, polyimide, polycarbonate, or the like, for example. Inaddition, the spacer may be formed of a material similarly to the cellgap adjusting film or by using a color filter or the like. That is,layers of each color which are used for a color filter or a protrusionare stacked appropriately to function as a spacer.

By such the spacer 3401 and the spacer 3501, a certain cell gap betweenthe substrate over which the cell gap adjusting film is formed and theopposite substrate can be maintained. Note that in FIGS. 34 and 35, thetransparent electrodes 1601 and 1701 are formed over the oppositesubstrate, respectively.

In addition, the spacer 3401 and the spacer 3501, which are providedother than minimum necessary spacers to maintain a cell gap, may behigher or lower than the spacers, which maintain the cell gap.

A liquid crystal material in the invention is not limited to thevertically aligned liquid crystal. A horizontally aligned liquidcrystal, a TN liquid crystal, an IPS liquid crystal, or a ferroelectricliquid crystal may be employed.

Note that description in this embodiment mode can commonly used for thedescription in Embodiment Modes 1 to 9. Therefore, the description inEmbodiment Modes 1 to 9 can be combined with the description in thisembodiment mode.

Embodiment Mode 11

In this embodiment mode, description is made of a method formanufacturing a semiconductor device by using plasma treatment as for amethod for manufacturing a semiconductor device including a transistor.

FIGS. 36A to 36C show views of a structural example of a semiconductordevice including a transistor. Note that FIG. 36B corresponds to a crosssectional view taken a line a-b in FIG. 36A, and FIG. 36C corresponds toa cross-sectional view taken a line c-d in FIG. 36A.

A semiconductor device shown in FIG. 36A to 36C includes a semiconductorfilm 4603 a and a semiconductor film 4603 b which are formed over asubstrate 4601 with an insulating film 4602 sandwiched therebetween, agate electrode 4605 which is formed over the semiconductor film 4603 aand the semiconductor film 4603 b with an gate insulating film 4604sandwiched therebetween, an insulating film 4606 and an insulating film4607 which are formed to cover the gate electrode, a conductive film4608 which is electrically connected to a source region or a drainregion of the semiconductor film 4603 a and the semiconductor film 4603b and formed over the insulating film 4607. Note that although FIGS. 36Ato 36C show the case where an n-channel transistor 4610 a which uses apart of the semiconductor film 4603 a as a channel region and ap-channel transistor 4610 b which uses a part of the semiconductor film4603 b as a channel region are provided, a structure is not limited tothis. For example, in FIGS. 36A to 36C, although an LDD region isprovided in the n-channel transistor 4610 a and is not provided in thep-channel transistor 4610 b, a structure in which LDD regions areprovided in both transistors or a structure in which an LDD region isprovided in neither of the transistors can be applied.

Note that in this embodiment mode, the semiconductor device shown inFIGS. 36A to 36C is manufactured by oxidizing or nitriding at least onelayer of the substrate 4601, the insulating film 4602, the semiconductorfilm 4603 a, the semiconductor film 4603 b, the gate insulating film4604, the insulating film 4606 and the insulating film 4607 by plasmatreatment so as to oxidize or nitride a semiconductor film or aninsulating film. By oxidizing or nitriding the semiconductor film or theinsulating film by plasma treatment in such a manner, a surface of thesemiconductor film or the insulating film is modified, and theinsulating film can be formed to be denser than an insulating filmformed by a CVD method or a sputtering method; therefore, a defect suchas a pinhole can be reduced, and characteristics and the like of thesemiconductor device can be improved.

Note that in this embodiment mode, description id made of a method formanufacturing a semiconductor device by performing plasma treatment onthe semiconductor films 4603 a and 4603 b, or the gate insulating film4604 in FIGS. 36A to 36C and oxidizing or nitriding the semiconductorfilms 4603 a and 4603 b, or the gate insulating film 4604, withreference to drawings.

As for an island-shaped semiconductor film which is formed over asubstrate, description is made of the case where an edge portion of theisland-shaped semiconductor film is provided with a shape close to aright-angled shape.

First, the island-shaped semiconductor films 4603 a and 4603 b areformed over the substrate 4601 (FIG. 37A). The island-shapedsemiconductor films 4603 a and 4603 b can be provided by forming anamorphous semiconductor film, which is formed of a material includingsilicon (Si) as a main component (for example, Si_(x)Ge_(1-x), or thelike) or the like, by using a sputtering method, an LPCVD method, aplasma CVD method, or the like over the insulating film 4602 which isformed in advance over the substrate 4601, by crystallizing theamorphous semiconductor film, and by etching a part of the semiconductorfilm. Note that crystallization of the amorphous semiconductor film canbe performed by a crystallization method such as a laser crystallizationmethod, a thermal crystallization method using RTA or an annealingfurnace, a thermal crystallization method using a metal element whichpromotes crystallization, a method of a combination thereof, or thelike. Note that in FIGS. 37A to 37D, edge portions of the island-shapedsemiconductor films 4603 a and 4603 b are formed to have an angle ofabout 90 degrees (θ=85 to 100 degrees). Note that an angle θ denotes anangle of a semiconductor film side, which is formed by a side face ofthe island-shaped semiconductor film and the insulating film 4602.

Next, oxide films or nitride films 4621 a and 4621 b (hereinafter alsoreferred to as an insulating film 4621 a and an insulating film 4621 b)are formed on surfaces of the semiconductor films 4603 a and 4603 b byoxidizing or nitriding the semiconductor films 4603 a and 4603 b byplasma treatment (FIG. 37B). For example, in the case where Si is usedfor the semiconductor films 4603 a and 4603 b, silicon oxide (SiO_(x))or silicon nitride (SiN_(x)) is formed as the insulating film 4621 a andthe insulating film 4621 b. In addition, the semiconductor films 4603 aand 4603 b may be oxidized by plasma treatment, and then may be nitridedby performing plasma treatment again. In that case, silicon oxide(SiO_(x)) is formed in contact with the semiconductor films 4603 a and4603 b, and silicon nitride oxide (SiN_(x)O_(y)) (x>y) is formed on thesurface of the silicon oxide. Note that in the case where thesemiconductor film is oxidized by plasma treatment, the plasma treatmentis performed in an oxygen atmosphere (for example, in an atmosphere ofoxygen (O₂) and at least one of an inert gas (He, Ne, Ar, Kr, Xe), in anatmosphere of oxygen, hydrogen (H₂), and an inert gas, or in anatmosphere of dinitrogen mono-oxide and an inert gas). On the otherhand, in the case the semiconductor film is nitrided by plasmatreatment, the plasma treatment is performed in a nitrogen atmosphere(for example, in an atmosphere of nitrogen (N₂) and at least one of aninert gas (He, Ne, Ar, Kr, Xe), in an atmosphere of nitrogen, hydrogen,and an inert gas, or in an atmosphere of NH₃ and an inert gas). As aninert gas, Ar may be used, for example. Further, a gas nixed with Ar andKr may be used. Therefore, the insulating films 4621 a and 4621 binclude an inert gas (including as least one of He, Ne, Ar, Kr, Xe)which is used for plasma treatment. In the case where Ar is used, theinsulating films 4621 a and 4621 b include Ar.

In addition, the plasma treatment is performed in the atmospherecontaining the aforementioned gas, with conditions of a plasma electrondensity ranging from 1×10¹¹ to 1×10¹³ cm⁻³, and a plasma electrontemperature ranging from 0.5 to 1.5 eV. Since the plasma electrondensity is high and the electron temperature in the vicinity of atreatment subject (here, the semiconductor films 4603 a and 4603 b)formed over the substrate 4601 is low, damage by plasma to the treatmentsubject can be prevented. In addition, since the plasma electron densityis as high as 1×10¹¹ cm⁻³ or more, an oxide film or a nitride filmformed by oxidizing or nitriding the treatment subject by plasmatreatment is superior in its uniformity of thickness and the like aswell as being dense, as compared with a film formed by a CVD method, asputtering method, or the like. Further, since the plasma electrontemperature is as low as 1 eV or less, oxidation or nitridation can beperformed at a lower temperature, compared with a conventional plasmatreatment or thermal oxidation. For example, oxidation or nitridationcan be performed sufficiently even when plasma treatment is performed ata temperature lower than a strain point of a glass substrate by 100degrees or more. Note that as a frequency for generating plasma, a highfrequency wave such as a microwave (2.45 GHz) can be used. Note that theplasma treatment is performed using the aforementioned conditions unlessotherwise specified.

Next, the gate insulating film 4604 is formed so as to cover theinsulating films 4621 a and 4621 b (FIG. 37C). The gate insulating film4604 can be formed by a sputtering method, an LPCVD method, a plasma CVDmethod, or the like, and provided with a single-layer structure or astacked-layer structure of an insulating film including oxygen ornitrogen, such as silicon oxide (SiO_(x)), silicon nitride (SiN_(x)),silicon oxynitride (SiO_(x)N_(y)) (x>y), or silicon nitride oxide(SiN_(x)O_(y)) (x>y). For example, in the case where Si is used for thesemiconductor films 4603 a and 4603 b, and Si is oxidized by plasmatreatment to form silicon oxide as the insulating films 4621 a and 4621b on the surfaces of the semiconductor films 4603 a and 4603 b, siliconoxide (SiO_(x)) is formed as the gate insulating film over theinsulating films 4621 a and 4621 b. In addition, in FIG. 37B, in thecase where the insulating films 4621 a and 4621 b which are formed byoxidizing or nitriding the semiconductor films 4603 a and 4603 b byplasma treatment are sufficiently thick, the insulating films 4621 a and4621 b can be used as gate insulating films.

Next, by forming the gate electrode 4605 and the like over the gateinsulating film 4604, a semiconductor device including the n-channeltransistor 4610 a and the p-channel transistor 4610 b which use theisland-shaped semiconductor films 4603 a and 4603 b as channel regionscan be manufactured (FIG. 37D).

In this manner, by oxidizing or nitriding the surfaces of thesemiconductor films 4603 a and 4603 b by plasma treatment beforeproviding the gate insulating film 4604 over the semiconductor films4603 a and 4603 b, a short circuit between the gate electrode and thesemiconductor films, which may be caused by a coverage defect of thegate insulating film 4604 at edge portions 4651 a and 4651 b of thechannel regions, or the like can be prevented. That is, in the casewhere the edge portions of the island-shaped semiconductor films have anangle of about 90 degrees (θ=85 to 100 degrees), the edges of thesemiconductor films might not be properly covered with a gate insulatingfilm when the gate insulating film is formed to cover the semiconductorfilm by a CVD method, a sputtering method, or the like. However, such acoverage defect and the like of the gate insulating film at the edges ofthe semiconductor films can be prevented by oxidizing or nitriding thesurfaces of the semiconductor films by plasma treatment in advance.

In addition, in FIGS. 37A to 37D, the gate insulating film 4604 may beoxidized or nitrided by further performing plasma treatment afterforming the gate insulating film 4604. In this case, an oxide film or anitride film 4623 (hereinafter also referred to as an insulating film4623) is formed on the surface of the gate insulating film 4604 (FIG.38B) by oxidizing or nitriding the gate insulating film 4604 byperforming plasma treatment to the gate insulating film 4604 which isformed to cover the semiconductor films 4603 a and 4603 b (FIG. 38A).The plasma treatment can be performed under similar conditions to thosein FIG. 37B. In addition, the insulating film 4623 includes an inert gaswhich is used for the plasma treatment, and for example, includes Ar inthe case where Ar is used for the plasma treatment.

In addition, in FIG. 38B, the gate insulating film 4604 is oxidized byperforming plasma treatment in an oxygen atmosphere once, and afterthat, may be nitrided by plasma treatment in a nitrogen atmosphere. Inthis case, silicon oxide (SiO_(x)) or silicon oxynitride (SiO_(x)N_(y))(x>y) is formed on the semiconductor films 4603 a and 4603 b side, andsilicon nitride oxide (SiN_(x)O_(y)) (x>y) is formed to be in contactwith the gate electrode 4605. Subsequently, by forming the gateelectrode 4605 and the like over the insulating film 4623, asemiconductor device having the n-channel transistor 4610 a and thep-channel transistor 4610 b which have the island-shaped semiconductorfilms 4603 a and 4603 b as channel regions can be manufactured (FIG.38C). In this manner, by oxidizing or nitriding the surface of the gateinsulating film by plasma treatment, the surface of the gate insulatingfilm can be modified to form a dense film. The insulating film obtainedby plasma treatment is denser and has fewer defects such as a pinhole ascompared with an insulating film formed by a CVD method or a sputteringmethod. Therefore, the characteristics of the transistors can beimproved.

Note that although FIG. 38A to 38C show the case where the surfaces ofthe semiconductor films 4603 a and 4603 b are oxidized or nitrided byperforming plasma treatment to the semiconductor films 4603 a and 4603 bin advance, a method where plasma treatment is performed after formingthe gate insulating film 4604 without performing to the semiconductorfilms 4603 a and 4603 b may be employed. In this manner, by performingplasma treatment before forming the gate electrode, an exposed portionof the semiconductor film due to a coverage defect can be oxidized ornitrided even if a coverage defect such as breaking of a gate insulatingfilm is caused at edge portions of the semiconductor film; therefore, ashort circuit between the gate electrode and the semiconductor film,which is caused by a coverage defect of the gate insulating film at theedges of the semiconductor film, or the like can be prevented.

In this manner, even in the case where the island-shaped semiconductorfilms are formed to have edges with an angle of about 90 degrees, ashort circuit between the gate electrodes and the semiconductor films,which is caused by a coverage defect of the gate insulating film at theedges of the semiconductor films, or the like can be prevented byoxidizing or nitriding the semiconductor films or the gate insulatingfilm by plasma treatment.

Next, as for the island-shaped semiconductor films formed over thesubstrate, FIGS. 39A to 39D show the case where the edge portions of theisland-shaped semiconductor films are provided with a tapered shape(θ=30 to 85 degrees).

First, the island-shaped semiconductor films 4603 a and 4603 b areformed over the substrate 4601 (FIG. 39A). The island-shapedsemiconductor films 4603 a and 4603 b can be provided by forming anamorphous semiconductor film, which is formed of a material includingsilicon (Si) as a main component (for example, Si_(x)Ge_(1-x), or thelike) and the like, by using a sputtering method, an LPCVD method, aplasma CVD method, or the like over the insulating film 4602 which isformed in advance over the substrate 4601, by crystallizing theamorphous semiconductor film by a crystallization method such as a lasercrystallization method, a thermal crystallization method using RTA or anannealing furnace, a thermal crystallization method using a metalelement which promotes crystallization, or a method of a combinationthereof, and by etching and removing a part of the semiconductor film.Note that in FIGS. 39A to 39D, the edge portions of the island-shapedsemiconductor films 4603 a and 4603 b are provided to have a taperedshape (θ=30 to 85 degrees).

Next, the gate insulating film 4604 is formed so as to cover thesemiconductor films 4603 a and 4603 b (FIG. 39B). The gate insulatingfilm 4604 can be provided to have a single-layer structure or astacked-layer structure of an insulating film containing oxygen ornitrogen, such as silicon oxide (SiO_(x)), silicon nitride (SiN_(x)),silicon oxynitride (SiO_(x)N_(y)) (x>y), or silicon nitride oxide(SiN_(x)O_(y)) (x>y) by a sputtering method, an LPCVD method, a plasmaCVD method, or the like.

Next, an oxide film or a nitride film 4624 (hereinafter also referred toas an insulating film 4624) is formed on the surface of the gateinsulating film 4604 by oxidizing or nitriding the gate insulating film4604 by plasma treatment (FIG. 39C). The plasma treatment can beperformed under similar conditions to the aforementioned description.For example, in the case where silicon oxide (SiO_(x)) or siliconoxynitride (SiO_(x)N_(y)) (x>y) is used as the gate insulating film4604, the gate insulating film 4604 is oxidized by performing plasmatreatment in an oxygen atmosphere, thereby a dense insulating film withfew defects such as a pinhole can be formed on the surface of the gateinsulating film in comparison with a gate insulating film formed by aCVD method, a sputtering method, or the like. On the other hand, if thegate insulating film 4604 is nitrided by plasma treatment in a nitrogenatmosphere, silicon nitride oxide (SiN_(x)O_(y)) (x>y) can be providedas the insulating film 4624 on the surface of the gate insulating film4604. Further, the gate insulating film 4604 is oxidized by performingplasma treatment in an oxygen atmosphere once, and after that, may benitrided by plasma treatment in a nitrogen atmosphere. In addition, theinsulating film 4624 includes an inert gas which is used for the plasmatreatment, and for example, includes Ar in the case where Ar is used.

Next, by forming the gate electrode 4605 and the like over the gateinsulating film 4604, a semiconductor device including the n-channeltransistor 4610 a and the p-channel transistor 4610 b which use theisland-shaped semiconductor films 4603 a and 4603 b as channel regionscan be manufactured (FIG. 39D).

In this manner, by performing plasma treatment to the gate insulatingfilm, the insulating film formed of an oxide film or a nitride film canbe provided on the surface of the gate insulating film, and the surfaceof the gate insulating film can be modified. The insulating filmobtained by oxidation or nitridation with plasma treatment is denser andhas fewer defects such as a pinhole as compared with a gate insulatingfilm formed by a CVD method or a sputtering method; therefore, thecharacteristics of the transistors can be improved In addition, while ashort circuit between the gate electrodes and the semiconductor films,which is caused by a coverage defect of the gate insulating film at theedges of the semiconductor films, or the like can be suppressed byforming the semiconductor films to have a tapered shape, a short circuitor the like between the gate electrodes and the semiconductor films canbe prevented even more effectively by performing plasma treatment afterforming the gate insulating film.

Next, description is made of a manufacturing method of a semiconductordevice which is different from that in FIGS. 39A to 39D with referenceto FIGS. 40A to 40D. Specifically, a case is shown where plasmatreatment is selectively performed to semiconductor films having atapered shape.

First, the island-shaped semiconductor films 4603 a and 4603 b areformed over the substrate 4601 (FIG. 40A). The island-shapedsemiconductor films 4603 a and 4603 b can be provided by forming anamorphous semiconductor film over the insulating film 4602 which isformed over the substrate 4601 in advance, by a sputtering method, anLPCVD method, a plasma CVD method, or the like, using a materialcontaining silicon (Si) as a main component (e.g., Si_(x)Ge_(1-x)) orthe like, crystallizing the amorphous semiconductor film and providingresists 4625 a and 4625 b used as masks for etching the semiconductorfilm selectively. Note that crystallization of the amorphoussemiconductor film can be performed by a laser crystallization method, athermal crystallization method using RTA or an annealing furnace, athermal crystallization method using metal elements which promotecrystallization, or a combination of these methods.

The edge portions of the island-shaped semiconductor films 4603 a and4603 b are selectively oxidized or nitrided by plasma treatment beforeremoving the resists 4625 a and 4625 b which are used for etching thesemiconductor films, thereby an oxide film or a nitride film 4626(hereinafter also referred to as an insulating film 4626) is formed oneach edge portion of the semiconductor films 4603 a and 4603 b (FIG.40B). The plasma treatment is performed under the aforementionedconditions. In addition, the insulating film 4626 contains an inert gaswhich is used for the plasma treatment.

The gate insulating film 4604 is formed to cover the semiconductor films4603 a and 4603 b after the resist 4625 a and 4625 b are removed (FIG.40C). The gate insulating film 4604 can be formed in a similar manner tothe above description.

By forming the gate electrodes 4605 and the like over the gateinsulating film 4604, a semiconductor device having the n-channeltransistor 4610 a and the p-channel transistor 4610 b which have theisland-shaped semiconductor films 4603 a and 4603 b as channel regionscan be manufactured (FIG. 40D).

When the edge portions of the semiconductor films 4603 a and 4603 b havetapered shapes, edge portions 4652 a and 4652 b of the channel regionswhich are formed in a part of the semiconductor films 4603 a and 4603 bare also tapered, thereby the thickness of the semiconductor films andthe gate insulating film in that portion are different from that in acentral portion, which may adversely affect the characteristics of thetransistors. However, such an effect on the transistors due to the edgeportions of the channel regions can be reduced by forming insulatingfilms on the edge portions of the semiconductor films, which are formedby selectively oxidizing or nitriding the edge portions of the channelregions by plasma treatment here.

Although FIGS. 40A to 40D show an example where only the edge portionsof the semiconductor films 4603 a and 4603 b are oxidized or nitrided byplasma treatment, the gate insulating film 4604 can also be oxidized ornitrided by plasma treatment as shown in FIGS. 39A to 39D (FIG. 42A).

Next, description is made of a manufacturing method of a semiconductordevice which is different from the aforementioned manufacturing methodwith reference to FIGS. 41A to 41D. Specifically, a case is shown whereplasma treatment is performed to semiconductor films with taperedshapes.

First, the island-shaped semiconductor films 4603 a and 4603 b areformed over the substrate 4601 in a similar manner to the abovedescription (FIG. 41A).

The semiconductor films 4603 a and 4603 b are oxidized or nitrided byplasma treatment, thereby forming oxide films or nitride films(hereinafter also referred to as insulating films 4627 a and 4627 b) onthe surfaces of the semiconductor films 4603 a and 4603 b respectively(FIG. 41B). The plasma treatment can be similarly performed under theaforementioned conditions. For example, when Si is used for thesemiconductor films 4603 a and 4603 b, silicon oxide (SiO_(x)) orsilicon nitride (SiN_(x)) is formed as the insulating films 4627 a and4627 b. In addition, after oxidizing the semiconductor films 4603 a and4603 b by plasma treatment, plasma treatment may be performed again tothe semiconductor films 4603 a and 4603 b, so as to be nitrided. In thiscase, silicon oxide (SiO_(x)) or silicon oxynitride (SiO_(x)N_(y)) (x>y)is formed on the semiconductor films 4603 a and 4603 b, and siliconnitride oxide (SiN_(x)O_(y)) (x>y) is formed on the surface of thesilicon oxide. Therefore, the insulating films 4627 a and 4627 b containan inert gas which is used for the plasma treatment. Note that the edgeportions of the semiconductor films 4603 a and 4603 b are simultaneouslyoxidized or nitrided by performing plasma treatment.

The gate insulating film 4604 is formed to cover the insulating films4627 a and 4627 b (FIG. 41C). The gate insulating film 4604 can beformed to have a single-layer structure or a stacked-layer structure ofan insulating film containing oxygen or nitrogen, such as silicon oxide(SiO_(x)), silicon nitride (SiN_(x)), silicon oxynitride (SiO_(x)N_(y))(x>y), or silicon nitride oxide (SiN_(x)O_(y)) (x>y) by a sputteringmethod, an LPCVD method, a plasma CVD method, or the like. For example,when Si is used for the semiconductor films 4603 a and 4603 b, and thesurfaces of the semiconductor films 4603 a and 4603 b are oxidized byplasma treatment to form silicon oxide as the insulating films 4627 aand 4627 b, silicon oxide (SiO_(x)) is formed as a gate insulating filmover the insulating films 4627 a and 4627 b.

By forming the gate electrodes 4605 and the like over the gateinsulating film 4604, a semiconductor device having the n-channeltransistor 4610 a and the p-channel transistor 4610 b which have theisland-shaped semiconductor films 4603 a and 4603 b as channel regionscan be manufactured (FIG. 41D).

When the edge portions of the semiconductor films have tapered shape,edge portions 4653 a and 4653 b of the channel regions which are formedin a part of the semiconductor films are also tapered, which mayadversely affect the characteristics of the semiconductor elements. Thesemiconductor films are oxidized or nitrided by plasma treatment, andaccordingly the edge portions of the channel regions are also oxidizedor nitrided; therefore, such an effect on the semiconductor elements canbe reduced.

Although FIGS. 41A to 41D show an example where only the semiconductorfilms 4603 a and 4603 b are oxidized or nitrided by plasma treatment, itis needless to say that the gate insulating film 4604 can be oxidized ornitrided by plasma treatment as shown in FIGS. 39A to 39D (FIG. 42B). Inthis case, after oxidizing the gate insulating film 4604 by plasmatreatment under an oxygen atmosphere, plasma treatment may be performedagain to the gate insulating film 4604 so as to be nitrided. In such acase, silicon oxide (SiO_(x)) or silicon oxynitride (SiO_(x)N_(y)) (x>y)is formed on the semiconductor films 4603 a and 4603 b, and siliconnitride oxide (SiN_(x)O_(y)) (x>y) is formed to be in contact with thegate electrodes 4605.

In addition, by performing plasma treatment in the aforementionedmanner, impurities such as dust attached to the semiconductor film andthe insulating film can be easily removed. In general, dust (alsoreferred to as a particle) is sometimes attached to the film formed by aCVD method, a sputtering method, or the like. For example, as shown inFIG. 43A, dust 4673 is sometimes formed over an insulating film 4672formed by a CVD method, a sputtering method, or the like, which isformed over a film 4671 such as an insulating film, a conductive film,or a semiconductor film. Even in such a case, the insulating film 4672is oxidized or nitrided by the plasma treatment and an oxide film or anitride film 4674 (hereinafter also referred to as an insulating film4674) is formed over the surface of the insulating film 4672. As for theinsulating film 4674, a portion under the dust 4673 as well as a portionin which the dust 4673 does not exist is oxidized or nitrided, and thusthe volume of the insulating film 4674 is increased. The surface of thedust 4673 is also oxidized or nitrided by the plasma treatment to forman insulating film 4675, and as a result, the volume of the dust 4673 isalso increased (FIG. 43B).

At this time, the dust 4673 can be easily removed from the surface ofthe insulating film 4674 by simple cleaning such as brush cleaning. Inthis manner, by performing plasma treatment, even minute dust attachedto the insulating film or a semiconductor film can be removed easily.Note that this effect is obtained by performing plasma treatment, andcan be applied to other embodiment modes as well as this embodimentmode.

As described above, by modifying the surface of the semiconductor filmor the gate insulating film by oxidizing or nitriding by plasmatreatment, a dense insulating film with good film quality can be formed.In addition, dust and the like attached to the surface of the insulatingfilm can be removed easily by cleaning. Consequently, even when theinsulating film is formed to be thinner, a defect such as a pinhole canbe avoided, and miniaturization and higher performance of asemiconductor element such as a transistor can be realized.

Although this embodiment mode shows an example where plasma treatment isperformed to the semiconductor films 4603 a and 4603 b, or the gateinsulating film 4604 shown in FIGS. 36A to 36C so as to oxidize ornitride the semiconductor films 4603 a and 4603 b, or the gateinsulating film 4604, a layer to be oxidized or nitrided by plasmatreatment is not limited to these. For example, plasma treatment may beperformed to the substrate 4601 or the insulating film 4602, or to theinsulating film 4606 or the insulating film 4607.

Note that description in this embodiment can be implemented freely incombination with those in Embodiment Modes 1 to 10.

Embodiment Mode 12

In this embodiment mode, description is made of a pixel structureincluded in a display device with reference to FIGS. 49A to 49F. Each ofpixels shown in FIGS. 49A to 49F includes a transistor 490, a liquidcrystal element 491, and a storage capacitor 492. A first electrode (oneof a source electrode and a drain electrode) of the transistor 490 isconnected to a source signal line 500. A second electrode (the other ofthe source electrode and the drain electrode) thereof is connected to apixel electrode of the liquid crystal element 491 and a first electrodeof the storage capacitor 492. A gate electrode of the transistor 490 isconnected to a gate line 501. A second electrode of the storagecapacitor 492 is connected to a capacitor line 502. Note that the liquidcrystal element includes the pixel electrode, a liquid crystal layer, anopposite electrode 493 and a cell gap adjusting film.

An analog voltage signal (video signal) is supplied to the source signalline 500. Note that the video signal may be a digital voltage signal ora current signal.

An H-level or L-level voltage signal (video signal) is supplied to thegate line 501. Note that in the case of using an n-channel transistor asthe transistor 490, the H level voltage signal is a voltage which canturn on the transistor 490, and the L level voltage signal is a voltagewhich can turn off the transistor 490. On the other hand, in the case ofusing a p-channel transistor as the transistor 490, the L level voltagesignal is a voltage which can turn on the transistor 490, and the Hlevel voltage signal is a voltage which can turn off the transistor 490.

Note that a certain power supply voltage is applied to the capacitorline 502. Note that a pulsing signal may be supplied to the capacitorline 502.

Description is made of an operation of a pixel in FIG. 49A. Here,description is made of the case using an n-channel transistor as thetransistor 490. First, when the gate line 501 becomes H level, thetransistor 490 is turned on, and the video signal is supplied to a firstelectrode of the liquid crystal element 491 and the first electrode ofthe storage capacitor 492 from the source signal line 500 thorough thetransistor 490 which is in an on state. A potential difference between apotential of the capacitor line 502 and a potential of the video signalis held by the storage capacitor 492.

Next, when the gate line 501 becomes L level, the transistor 490 isturned off, and the source signal line 500 and the first electrode ofthe liquid crystal element 491 and the first electrode of the storagecapacitor 492 are electrically disconnected. However, the potentialdifference between the potential of the capacitor line 502 and thepotential of the video signal is held by the storage capacitor 492;therefore, a potential of the first electrode of the storage capacitor492 can be held as similar potential as the video signal. Therefore, apotential of the first electrode of the liquid crystal electrode 491 canbe held to be equal to that of the video signal.

As described above, luminance can be controlled depending ontransmittance of the liquid crystal element 491 in accordance with thevideo signal.

Note that although not shown in the drawings, the storage capacitor 492is not necessarily required if the liquid crystal element 491 includes acapacitance component enough to hold the video signal.

In addition, the liquid crystal element 491 is a semi-transmission typeliquid crystal element including the reflection region and thetransmission region. In the reflection region and the transmissionregion, cell gaps are different depending on a cell gap adjusting film.By using the cell gap adjusting film, a viewing angle can be increasedwhen displaying an image and deterioration of image quality due todisorder of orientation of the liquid crystal can be controlled;therefore, a semi-transmission type liquid crystal display device withhigh display quality can be obtained.

In addition, as shown in FIG. 49B, one pixel may be formed by twosub-pixels 511 a and 511 b. Here, the capacitor line 502 is commonlyused by the sub-pixel 511 a and the sub-pixel 511 b. Further, both aliquid crystal element 512 and a liquid crystal element 513 may be theaforementioned liquid crystal elements 491, that is, thesemi-transmission type liquid crystal elements including the reflectionregion and the transmission region, or either one may be.

As described above, by dividing one pixel into sub-pixels, a differentvoltage can be applied to each sub-pixel. Therefore, area gray scaledisplay can be performed, and a viewing angle can be further increasedby using a difference of orientation of the liquid crystal in eachsub-pixel.

In addition, the gate line 501 may be used as a common wire as shown inFIG. 49C instead of using the capacitor line 502 as a common wirebetween sub-pixels as shown in FIG. 49B. Further, the gate line 501 andthe capacitor line 502 may be used as common wires between thesub-pixels, and the source signal lines 500 a and 500 b may be providedin each sub-pixel.

In addition, a structure where a pixel includes two liquid crystalelements 512 and 513 as shown in FIGS. 49E and 49F instead of dividingone pixel into a plurality of sub-pixels may be used.

Note that description in this embodiment can be implemented freely incombination with those in Embodiment Modes 1 to 11. In addition, a pixelstructure of a display device of the invention is not limited to thosedescribed above.

Embodiment Mode 13

FIG. 44 shows a structural example of a portable phone including adisplay portion for which a display device of the invention and thedisplay device using the driving method thereof are employed.

A display panel 5410 is detachably incorporated into a housing 5400. Ashape and size of the housing 5400 can be appropriately changed inaccordance with a size of the display panel 5410. The housing 5400 whichfixes the display panel 5410 is fit into a printed board 5401 andassembled as a module.

The display panel 5410 is connected to the printed board 5401 through anFPC 5411. A speaker 5402, a microphone 5403, a transmission/receptioncircuit 5404, and a signal processing circuit 5405 including a CPU, acontroller and the like are formed over the printed board 5401. Such amodule is combined with an input unit 5406 and a battery 5407, andstored using a chassis 5409 and a chassis 5412. A pixel portion of thedisplay panel 5410 is provided so as to be seen from an open windowformed in the housing 5412.

The display panel 5410 may be formed in such a manner that a pixelportion and a part of peripheral driver circuits (a driver circuit witha low operating frequency among a plurality of driver circuits) areformed over a substrate by using TFTs, while another part of theperipheral driver circuits (a driver circuit with a high operatingfrequency among the plurality of driver circuits) is formed over an ICchip, which may be mounted on the display panel 5410 by COG (Chip OnGlass). Alternatively, the IC chip may be connected to a glass substrateby TAB (Tape Automated Bonding) or by using a printed board. Note thatFIGS. 45A and 45B show examples of a structure of a display panel, inwhich a part of peripheral driver circuits and a pixel portion areformed over a substrate, while another part of the peripheral drivercircuits is formed in an IC chip to be mounted on the substrate by COGor the like.

In FIG. 45A, a pixel portion 5302 and peripheral driver circuits (afirst scan line driver circuit 5303 and a second scan line drivercircuit 5304) may be formed over a substrate 5300 of a display panel,and a signal line driver circuit 5301 may be formed over the IC chip andmounted on the display panel by COG or the like. Note that the pixelportion 5302 and the peripheral driver circuits which are formedintegrally over the substrate are sealed by using a sealing member 5309to bond a sealing substrate 5308 and the substrate 5300 together. Inaddition, IC chips (semiconductor chips formed of a memory circuit, abuffer circuit, and the like) 5306 and 5307 may be mounted over aconnection portion of an FPC 5305 and the display panel by COG or thelike. Note that although only an FPC is shown in the drawings, a printedwiring board (PWB) may be mounted on the FPC.

As described above, only a signal line driver circuit, which is requiredto operate with high speed, is formed over an IC chip by using a CMOS orthe like; therefore, a reduction in power consumption can be achieved.In addition, by using a semiconductor chip such as a silicon wafer as anIC chip, higher-speed operation and lower power consumption can beachieved. Further, the first scan line driver circuit 5303 and thesecond scan line driver circuit 5304 are formed integrally with thepixel portion 5302, and thereby cost reduction can be achieved. Inaddition, an IC chip formed by a functional circuit (a memory and abuffer) is mounted on a connection portion of the FPC 5305 and thesubstrate 5300, and thereby an area of the substrate can be usedeffectively.

In order to further reduce power consumption, all peripheral drivercircuits may be formed over an IC chip, and the IC chip may be mountedon the display panel by COG or the like. For example, as shown in FIG.45B, a pixel portion 5312 may be formed over a substrate 5310. A signalline driver circuit 5311, a first scan line driver circuit 5313 and asecond scan line driver circuit 5314 may be formed over an IC chip andmounted on the display panel by COG or the like. Note that an FPC 5315,an IC chip 5316, an IC chip 5317, a sealing substrate 5318, and asealing member 5319 in FIG. 45B correspond to the FPC 5305, the IC chip5306, the IC chip 5307, the sealing substrate 5308, and the sealingmember 5309, respectively.

By using such a structure, power consumption of the display device canbe reduced, and operation time of a portable phone per charge can beextended. In addition, cost reduction of a portable phone can beachieved.

In addition, by converting an impedance of a signal set to a scan lineor a signal line by a buffer, time for writing a signal to pixels in onerow can be shortened. Therefore, a high-definition display device can beprovided.

In addition, in order to further reduce power consumption, a pixelportion is formed over a substrate with TFTs, and all the peripheralcircuits are formed over an IC chip, which may be mounted on the displaypanel by COG (Chip On Glass) or the like.

By using the display device of the invention, a clear and high-contrastimage can be provided.

Note that the structure shown in this embodiment mode is an example of amobile phone; therefore, the display device of the invention is notlimited to the mobile phone with the aforementioned structure, and canbe applied to mobile phones with various structures.

Note that description in this embodiment mode can be implemented freelyin combination with those in Embodiment Modes 1 to 12.

Embodiment Mode 14

FIG. 46 shows a liquid crystal module combined with a display panel 5701and a circuit substrate 5702. The display panel 5701 includes a pixelportion 5703, a scan line driver circuit 5704 and a signal line drivercircuit 5705. A control circuit 5706, a signal dividing circuit 5707,and the like are formed over the circuit substrate 5702, for example.The display panel 5701 and the circuit substrate 5702 are connected by aconnection wire 5708. An FPC or the like can be used for the connectionwire.

The order of appearance of subframes and the like are controlled bymainly the control circuit 5706.

The display panel 5701 may be formed in such a manner that a pixelportion and a part of peripheral driver circuits (a driver circuit witha low operating frequency among a plurality of driver circuits) areformed over a substrate by using TFTs, while another part of theperipheral driver circuits (a driver circuit with a high operatingfrequency among the plurality of driver circuits) is formed over an ICchip, which may be mounted on the display panel 5701 by COG (Chip OnGlass) or the like. Alternatively, the IC chip may be mounted on thedisplay panel 5701 by TAB (Tape Automated Bonding) or by using a printedboard. Note that FIG. 45A shows an example of a structure in which apart of peripheral driver circuits and a pixel portion are formed over asubstrate, while another part of the peripheral driver circuits isformed in an IC chip to be mounted on the substrate by COG or the like.By using such a structure, power consumption of the display device canbe reduced, and operation time of a portable phone per charge can beextended. In addition, cost reduction of a portable phone can beachieved.

In addition, by converting an impedance of a signal set to a scan lineor a signal line by a buffer, time for writing a signal to pixels in onerow can be shortened. Therefore, a high-definition display device can beprovided.

In addition, in order to further reduce power consumption, a pixelportion is formed over a glass substrate with TFTs, and all the signalline driver circuits are formed over an IC chip, which is mounted on thedisplay panel by COG (Chip On Glass).

Note that it is preferable that a pixel portion is formed over asubstrate by using TFTs, and all the peripheral driver circuits areformed over an IC chip, which may be mounted on the display panel by COG(Chip On Glass). Note that FIG. 45B shows an example of a structure inwhich a pixel portion is formed over a substrate, and an IC chip overwhich signal line driver circuit is formed is mounted on the substrateby COG or the like.

A liquid crystal television receiver can be completed with the liquidcrystal module. FIG. 47 is a block diagram showing a main structure ofthe liquid crystal television receiver. A tuner 5801 receives a videosignal and an audio signal. The video signal is processed by a videosignal amplifier circuit 5802, a video signal processing circuit 5803,which converts a signal outputted from the video signal amplifiercircuit 5802 to a color signal corresponding to each color of red, greenand blue, and a control circuit 5706 which converts the video signal toinput specifications of a driver circuit. The control circuit 5706outputs signals to each of a scan line side and a signal line side. Whenperforming digital drive, the signal dividing circuit 5707 may beprovided on the signal line side so that the inputted digital signal isdivided into m signals to be supplied.

Among the signals received by the tuner 5801, an audio signal istransmitted to an audio signal amplifier circuit 5804, and an outputthereof is supplied to a speaker 5806 through the audio signalprocessing circuit 5805. A control circuit 5807 receives control data ona receiving station (receive frequency) and volume from an input portion5808, and transmits the signal to the tuner 5801 and the audio signalprocessing circuit 5805.

A television receiver can be completed by incorporating a liquid crystalmodule into a housing. A display portion is formed by the liquid crystalmodule. In addition, a speaker, a video input terminal, and the like areprovided appropriately.

It is needless to say that the invention is not limited to a televisionreceiver, and can be applied to various uses such as a monitor of apersonal computer, an information display board at a train station or anairport, and an advertising display board on the street, specifically asa large-area display medium.

As described above, by using the display device of the invention, aclear and high-contrast image can be provided.

Note that description in this embodiment mode can be implemented freelyin combination with those in Embodiment Modes 1 to 13.

Embodiment Mode 15

The invention can be applied to various electronic apparatuses, andspecifically to a display portion of an electronic apparatus. As forsuch an electronic apparatus, a camera such as a video camera and adigital camera, a goggle type display, a navigation system, an audioreproducing device (a car audio, an audio component stereo, and thelike), a computer, a game machine, a portable information terminal (amobile computer, a portable phone, a portable game machine, anelectronic book, and the like), an image reproducing device providedwith a recording medium (specifically, a device for reproducing arecording medium such as a digital versatile disc (DVD) and having adisplay for displaying the reproduced image), and the like are taken forexample.

FIG. 48A shows a display device, which includes a chassis 35001, asupporting base 35002, a display portion 35003, speaker portions 35004,a video input terminal 35005, and the like. The display device of theinvention can be applied to the display portion 35003. Note that thedisplay device includes all information display devices such as thosefor a personal computer, TV broadcasting reception, and advertisementdisplay. A display device which uses the display device of the inventionfor the display portion 35003 can provide a clear and high-contrastimage.

FIG. 48B shows a camera, which includes a main body 35101, a displayportion 35102, an image receiving portion 35103, operating keys 35104,an external connecting port 35105, a shutter 35106, and the like.

A digital camera in which the invention is applied to the displayportion 35102 can be obtained a clear and high-contrast image.

FIG. 48C shows a computer, which includes a main body 35201, a chassis35202, a display portion 35203, a keyboard 35204, an external connectingport 35205, a pointing mouse 35206, and the like. A computer in whichthe invention is applied to the display portion 35203 can provide aclear and high-contrast image.

FIG. 48D shows a mobile computer, which includes a main body 35301, adisplay portion 35302, a switch 35303, operating keys 35304, an infraredport 35305, and the like. A mobile computer in which the invention isapplied to the display portion 35302 can provide a clear andhigh-contrast image.

FIG. 48E is a portable image reproducing device provided with arecording medium (specifically, a DVD player), which includes a mainbody 35401, a chassis 35402, a display portion A 35403, a displayportion B 35404, a recording medium (DVD and the like) reading portion35405, an operating key 35406, a speaker portion 35407, and the like.The display portion A 35403 mainly displays image data, while thedisplay portion B 35404 mainly displays text data. An image reproducingdevice in which the invention is applied to the display portions A 35403and B 35404 can provide a clear and high-contrast image can be obtained.

FIG. 48F shows a goggle type display, which includes a main body 35501,a display portion 35502, an arm portion 35503, and the like. A goggletype display in which the invention is applied to the display portion35502 can provide a clear and high-contrast image.

FIG. 48G shows a video camera, which includes a main body 35601, adisplay portion 35602, a chassis 35603, an external connecting port35604, a remote controller receiving portion 35605, an image receivingportion 35606, a battery 35607, an audio input portion 35608, operatingkeys 35609, and the like. A video camera in which the invention isapplied to the display portion 35602 can provide a clear andhigh-contrast image.

FIG. 48H shows a portable phone, which includes a main body 35701, achassis 35702, a display portion 35703, an audio input portion 35704, anaudio output portion 35705, an operating key 35706, an externalconnecting port 35707, an antenna 35708, and the like. A mobile phone inwhich the invention is applied to the display portion 35703 can providea clear and high-contrast image.

As described above, the applicable range of the invention is so widethat the invention can be applied to electronic apparatuses of variousfields. In addition, the electronic apparatuses in this embodiment modemay use a display device manufactured with any of the structures inEmbodiment Modes 1 to 14.

This application is based on Japanese Patent Application serial No.2005-303766 filed in Japan Patent Office on Oct. 18, 2005, the entirecontents of which are hereby incorporated by reference.

1. A liquid crystal display device comprising: a liquid crystal layer ina reflection region and a transmission region, interposed between afirst substrate and a second substrate; a film for adjusting a cell gapin the reflection region, interposed between the first substrate and theliquid crystal layer; a pixel electrode in the reflection region and thetransmission region, interposed between the first substrate and theliquid crystal layer; and an opposite electrode in the reflection regionand the transmission region, interposed between the liquid crystal layerand the second substrate; wherein: the pixel electrode in the reflectionregion and the transmission region includes a slit, the pixel electrodein the reflection region is provided over the film for adjusting thecell gap and reflects light, the pixel electrode in the transmissionregion transmits light, the slit is overlapped with at least a part of astep portion which is provided between the reflection region and thetransmission region by the film for adjusting the cell gap, and the slitis extended radially and obliquely with respect to one end portion ofthe pixel electrode.
 2. The liquid crystal display device according toclaim 1, wherein the pixel electrode in the reflection region has anuneven surface.
 3. The liquid crystal display device according to claim1, wherein a distance between a boundary portion of the film foradjusting the cell gap and the pixel electrode in the reflection regionis larger than a distance between a boundary portion of the film foradjusting the cell gap and the pixel electrode in the transmissionregion.
 4. The liquid crystal display device according to claim 1,wherein a width of the slit of the pixel electrode in the reflectionregion is larger than that of the slit of the pixel electrode in thetransmission region.
 5. The liquid crystal display device according toclaim 1, wherein a width of the slit of the pixel electrode in aboundary portion between the reflection region and the transmissionregion is larger than that of the slit of the pixel electrode in thereflection region.
 6. A liquid crystal display device comprising: aliquid crystal layer in a reflection region and a transmission region,interposed between a first substrate and a second substrate; a film foradjusting a cell gap in the reflection region, interposed between thefirst substrate and the liquid crystal layer; a pixel electrode in thereflection region and the transmission region, interposed between thefirst substrate and the liquid crystal layer; and an opposite electrodein the reflection region and the transmission region, interposed betweenthe liquid crystal layer and the second substrate; wherein: the pixelelectrode in the reflection region and the transmission region includesa first slit, the pixel electrode in the reflection region is providedover the film for adjusting the cell gap and reflects light, the pixelelectrode in the transmission region transmits light, the first slit isoverlapped with at least a part of a step portion which is providedbetween the reflection region and the transmission region by the filmfor adjusting the cell gap, the first slit is extended radially andobliquely with respect to one end portion of the pixel electrode, andthe opposite electrode includes a second slit.
 7. The liquid crystaldisplay device according to claim 6, wherein the pixel electrode in thereflection region has an uneven surface.
 8. The liquid crystal displaydevice according to claim 6, wherein a distance between a boundaryportion of the film for adjusting the cell gap and the pixel electrodein the reflection region is larger than a distance between a boundaryportion of the film for adjusting the cell gap and the pixel electrodein the transmission region.
 9. The liquid crystal display deviceaccording to claim 6, wherein a width of the first slit of the pixelelectrode in the reflection region is larger than that of the first slitof the pixel electrode in the transmission region.
 10. The liquidcrystal display device according to claim 6, wherein a width of thefirst slit of the pixel electrode in a boundary portion between thereflection region and the transmission region is larger than that of thefirst slit of the pixel electrode in the reflection region.
 11. Theliquid crystal display device according to claim 6, wherein a width ofthe second slit of the opposite electrode in the reflection region islarger than that of the second slit of the opposite electrode in thetransmission region.
 12. A liquid crystal display device comprising: aliquid crystal layer in a reflection region and a transmission region,interposed between a first substrate and a second substrate; a film foradjusting a cell gap in the reflection region, interposed between thefirst substrate and the liquid crystal layer; a pixel electrode in thereflection region and the transmission region, interposed between thefirst substrate and the liquid crystal layer; and an opposite electrodein the reflection region and the transmission region, interposed betweenthe liquid crystal layer and the second substrate; and a conductive filmin the reflection region interposed between the first substrate and thefilm for adjusting the cell gap; wherein: the pixel electrode in thereflection region and the transmission region includes a slit, the pixelelectrode in the reflection region is provided over the film foradjusting the cell gap and transmits light, the pixel electrode in thetransmission region transmits light, the slit is overlapped with atleast a part of a step portion which is provided between the reflectionregion and the transmission region by the film for adjusting the cellgap, the slit is extended radially and obliquely with respect to one endportion of the pixel electrode, and the conductive film reflects light.13. The liquid crystal display device according to claim 12, wherein thepixel electrode in the reflection region has an uneven surface.
 14. Theliquid crystal display device according to claim 12, wherein a distancebetween a boundary portion of the film for adjusting the cell gap andthe pixel electrode in the reflection region is larger than a distancebetween a boundary portion of the film for adjusting the cell gap andthe pixel electrode in the transmission region.
 15. The liquid crystaldisplay device according to claim 12, wherein a width of the slit of thepixel electrode in the reflection region is larger than that of the slitof the pixel electrode in the transmission region.
 16. The liquidcrystal display device according to claim 12, wherein a width of theslit of the pixel electrode in a boundary portion between the reflectionregion and the transmission region is larger than that of the slit ofthe pixel electrode in the reflection region.
 17. The liquid crystaldisplay device according to claim 12, wherein the conductive film has anuneven surface.
 18. The liquid crystal display device according to claim12, wherein the pixel electrode is electrically connected to theconductive film.
 19. The liquid crystal display device according toclaim 12, wherein a distance between a boundary portion of the film foradjusting the cell gap and the conductive film is smaller than adistance between a boundary portion of the film for adjusting the cellgap and the pixel electrode in the reflection region.